Dive Atlas Of The World: An Illustrated Reference To The Best Sites - Jack Jackson (2016)

DIVE ATLAS OF THE WORLD

INTRODUCTION

by Jack Jackson

TROPICAL ISLANDS, BEACHES, TURQUOISE SEAS AND COLOURFUL reefs attract non-divers, divers and snorkellers alike, but experienced divers also enjoy deep walls in open sea, interaction with marine animals, the bounty of cold waters and the atmosphere of shipwrecks.

Remaining shallow maximizes divers’ time in the water, but some divers favour short deep ‘bounces’, hoping to encounter sharks. While most divers prefer relaxing dives, some seek heart-thumping, shark feeding-frenzies or the adrenaline rush of high-voltage drift dives. Some divers prefer clear, warm water while others are happy with limited visibility or cold water. Wreck fanatics often ignore everything else. Whatever type of diving is preferred, most training agencies will offer a speciality course on how to enjoy it safely. Remember that deep dives, cold water and strong currents are physically demanding and conditions can change quickly, so always be prepared to abort a dive.

We have chosen popular sites for each region, with a good range of underwater environments and geographical coverage. Our criteria included quality, quantity, beauty and uniqueness of marine life, accessibility and the requirement of only a reasonable degree of physical fitness. The selection offered here celebrates the underwater world while appealing to a broad spectrum of active and armchair divers.

The book is organized according to oceans and regions within those oceans, beginning with the Atlantic and working west to east and north to south. Practical information is given in the directory appendix.

There is considerable diversity among diving destinations. Most temperate and warm water species or seawater and freshwater species do not mix. Where regions become isolated, either permanently or temporarily such as when ice ages lowered sea levels and cut off the Red Sea, Gulf of Aden and the Arabian Gulf from the Indian Ocean, some species evolve in isolation and become endemic to those regions. Coral reefs harbour many colourful species. Nutrient-rich, cold waters offer abundant marine life that is often larger and longer-living than its tropical counterpart. Some regions have large tidal ranges. Under ice, over rock or coral and over deep water visibility can be exceptional, but where there is a large tidal flow, a sandy or muddy bottom or a plankton bloom, visibility can be awful.

Most coral reef life evolved in what is now the region bordered by the Philippines, Malaysia and Papua New Guinea and then spread out to colonize other regions. The Atlantic Ocean formed late in geological time and, early in its development, was cut off from the Pacific by North and South America fusing together. The connecting ridges in the eastern Caribbean also prevent the interchange of deep water from the Atlantic into the Caribbean. Partly as a result of being cut off on west and east, the Caribbean has fewer marine species than the Indo-Pacific.

Many Caribbean countries have sophisticated ambience, extensive facilities, maximum water clarity, habituated animal encounters and often current-free diving, a package that is particularly attractive to divers on vacation. The Indo-Pacific has the greatest species diversity, though the high level of plankton that feeds this profusion of life often degrades visibility. Some Pacific areas have strong currents and one tide each day much stronger than the other.

SHORE DIVING

Entering the water from a beach or jetty is relatively simple, but climbing over slippery rocks in full diving gear can be difficult. When entering from the rocks of a slope or wall, divers will require knowledge of the local tides because low water could result in a large drop into the water and a height too great for divers to be able to exit the water. There may be long swims across fringing reefs and photographers have extra problems with grit. Shore diving is cheaper than day-boat diving, but most of the accessible sites are not as good as those on offshore reefs.

DAY-BOAT DIVING

Day boats leave the shore for near-shore dive sites once or twice a day (few operators offer three per day). Night dives are optional. Frequently, equipment needs to be carried to and from the beach or jetty. As with any form of boat diving someone must be delegated to ensure that everyone who should be on board is on board when it departs and, most importantly, when it leaves the dive site.

In the case of an inflatable or small tender, divers will embark already kitted-up, except for fins. On larger boats divers will kit up about 15 minutes from the dive site.

Shore and day-boat diving are preferred by those who cannot sleep on a moving boat or are accompanied by non-diving partners or families and those with an interest in the local nightlife.

LIVE-ABOARD BOAT DIVING

With live-aboard diving there is less carrying of heavy equipment, no swimming over fringing reefs, biting insects are left behind when you leave port and sailing overnight maximizes the diving time on remote offshore sites. There are fewer restrictions on night dives and divers get three to five dives each day instead of heading back to shore after two dives. Photographers do not have to worry about sand damaging O-rings and have more time to sort out cameras between dives.

On the minus side, narrow boats and those that are high in the water roll about with the slightest swell or chop, some people cannot sleep on a moving boat and rough seas can be frightening. Live-aboards appear expensive, but you get more dives for your money and all food is included. You need to pack warmer clothing for the cooler conditions at sea.

While live-aboards may offer five dives per day, divers also have to think about tides, currents, personal nitrogen-loading, and the visibility on ebb tides can be poor. It is better to take fewer (quality) dives each day than five dives, of which some may be mediocre.

Most divers do not like to have large numbers of people in the water at the same time. Larger live-aboard boats should either have two tenders serving two separate dive sites, or have a rota system whereby only half of their clients are in the water at any one time.

There have been cases of live-aboard boats leaving divers in the water and sailing off without them, so make sure that the boat you use has a foolproof diver check-in and check-out system.

REEF DIVING, DROP-OFFS AND WALLS

Reefs may have several distinct profiles. The top of the reef is likely to be a coral garden with smaller species of fish and crustaceans. Slopes or drop-offs have larger gorgonias and larger fish in shoals. Walls combine the above and have larger pelagic species, especially when over deep water. A wall is near-vertical and may be overhanging or undercut, while drop-offs are steep slopes of 60-85°.

Inshore fringing reefs tend to have poor visibility due to pollution from construction, domestic or industrial waste or mud carried down rivers, but they are good study areas as they harbour immature species.

Where offshore reefs have lagoons, these are convenient for safe anchorage, muck diving and snorkelling, but many prefer the better diving outside the reef. Channels into lagoons are good places to dive when the current is running, because the nutrients it carries attract smaller fish, which in turn attract larger predators. Where one side of a reef is longer or more contorted than the other side, the current is slowed down more on that side. When the currents meet again at points on the lee end of the reef they are travelling at different speeds, producing whirlpools and upwellings full of nutrients that attract large shoals of fish. In turn these fish attract sharks and other predators. If you can find shelter from the current, these points are great places to dive.

DIVING IN FRESHWATER

The main difference between diving in seawater and diving in freshwater is that freshwater is less buoyant and there are few freshwater sites that are charted. Some freshwater sites will be at a high enough altitude to require the use of special dive tables and corrections to the measured depths. Heavy rain can reduce freshwater visibility to zero.

In some areas lakes are fed by hot springs and can get very hot!

Diving in lakes or flooded quarries is relatively easy, but diving in rivers can be difficult if they are fast flowing. In general the current will be slower near the riverbank due to the friction of the water against the bank, but you must always consider where you can exit the river before you enter it. Hooks can be used to pull yourself along the river bottom against the current.

Freshwater and brackish-water sites, particularly lakes, quarries, dams, canals and slow-flowing rivers, often carry infections such as Weil’s disease (Leptospirosis) and, in countries where it is endemic, Bilharzia (Schistosomiasis).

Some reefs are submerged and can only be found by a knowledgeable boat skipper or Global Positioning System. Divers have to descend quickly to the lee of the reef for shelter from the current before they get swept off. However, such reefs usually have top diving and pelagics.

DRIFT-DIVING

Drift-diving can vary from pleasantly drifting in a gentle current to high-voltage rushes as divers are swept along walls and gullies. The main concerns are good boat cover and becoming separated from div ing buddies. Divers not using surface marker buoys should carry a delayed deployment surface marker buoy or, better still, a high-visibility rescue tube or collapsible flag, which can be raised above the swell.

Insist that the chase-boat crew follow the surface marker buoy or divers’ bubbles and do not go to sleep or have loud music preventing them from hearing divers’ whistles when they surface. Power whistles are better at attracting the boat cover than manual whistles and an old CD can be used as a heliograph.

Buddies, and preferably the whole group, should enter the water together so that they do not get separated on the surface and they should try to keep together underwater. If divers do get separated from their boat cover, it is wise to tie a buddy line between each other, inflate the BCDs (Buoyancy Compensator Device) and conserve air. It is usually best to retain weight belts unless buoyancy is a problem; in certain circumstances it may be better to jettison the scuba cylinders.

Divers wanting to fin ashore while wearing a normal BCD rather than wings will find it less tiring to fin on their backs. At the shore, untie the buddy line before trying to swim through surf or breakers.

WRECK AND CAVE DIVING

When diving in enclosed overhead environments, it is not easy to reach the surface in the event of equipment failure.

Any level of diver can enjoy diving around a wreck, but penetrating large wrecks is advanced diving and novice divers should only attempt it when accompanied by an instructor. Plan dives to coincide with slack water and wear gloves for protection from sharp metal. Carry a sharp knife and a suitable monofilament line cutter or shears for cutting fishing line and nets. Have a good dive-light and carry another as backup. Make sure that equipment is streamlined against the diver’s body where it cannot snag.

Divers should tie off a guideline before penetration and feed it out as they go, tie back any doors or hatches, so that they cannot close in a current. Remember that exhaust bubbles disturb sediment, as do fins and hands. Leave plenty of air to get out of the wreck and back to the surface.

Cavern diving, where divers are always within sight of daylight, is not difficult. However, cave diving, beyond any source of daylight, requires a safety guideline so that the divers can find their way back to safety in zero visibility. They will also need separate backup sources of light and breathing-gasses. Most important is the rule of thirds: divers turn around when one-third of their breathing gas is used up, leaving one-third to find their way out and one-third for emergencies. Apart from exhaust bubbles disturbing sediment as they strike the roof, divers can minimize the disturbance of sediment by learning to use gentle, shallow fin-strokes.

NIGHT DIVING

For night dives, divers should choose a shallow dive with easy marks for navigation, with which they have already familiarized themselves in daylight. The easiest night dives are along reef edges, where divers can swim out along the face at one depth and return along it at a shallower depth. If there is a current divers should set out against it and return with it.

Avoid dive lights that are too powerful and carry a spare as a backup, but spend some time with your lights switched off. When your eyes are accustomed to the dark, wave your arms about and you will notice phosphorescent plankton and, in caves, you may spot the bioluminescence of flashlightfish.

TEMPERATE WATERS VERSUS TROPICAL WATERS

Many divers do most of their diving in temperate waters. Shipwrecks are the most popular sites, but the marine life can be just as interesting as in tropical waters. In general the visibility and surface conditions will not be that good. By contrast, when diving in the warm, clear water of the tropics, surrounded by colourful marine life, divers are likely to be more relaxed. The main danger with such clear water is that you are likely to dive deep without realizing it. Many of the more popular diving holiday destinations are in areas where tides and currents are minimal and sea conditions usually calm.

ICE DIVING

Always be prepared for equipment failure - even weightbelt buckles have failed. Although the water temperature cannot fall below -1.8°C (28.7°F), or it would be frozen solid, wind-chill can make air temperature many degrees colder. A full-face mask makes it difficult to access a backup regulator. Each diver should have two separate regulators, either on separate scuba cylinders or on a single one with a V-manifold. Cylinders should be filled with air that is as dry as possible. Cylinders and regulators should be stored out of the wind in a dry place until entering the water. Regulator first stages should be environmentally sealed against the ingress of water and not breathed through until both first and second stages are submerged to avoid condensation freezing the regulator. Divers should each be attached to a line strong enough for hauling them to the surface. Each line should be tied off securely and attended by someone doing nothing else, feeling for an agreed series of rope signals from the diver. Erratic pulls, unreadable pulls or no response, should be treated as an emergency and the diver pulled up.

Diving under ice is a surreal experience. The ice forms amazing shapes and at high latitudes the animals exhibit gigantism.

It is wise to wear thin exposure suits against creatures that sting, but the best chance of ruining your holiday comes from sunburn or insect bites when you are not diving.

ARCHAEOLOGICAL DIVING

Archaeological diving is usually restricted to academics but there are times when they are grateful for amateur help and some of the finds in the Egyptian Mediterranean are now open to guided diving tours. Where such sites are close to a port there will be sewage and industrial pollution in the water and oil on the surface. Divers should take a course of broad-spectrum antibiotic as a prophylactic against intestinal infections. Diesel oil on the surface causes skin-burns and degrades exposure-suit materials, so wash all equipment (and yourself) with freshwater immediately after immersion.

UNDERWATER VISIBILITY

In mid-oceanic waters the vertical visibility can reach 100m (328ft), but horizontal visibility greater than 50m (165ft) is mythical. Coastal waters are affected by rain, run-off, disturbed bottom sediment, agricultural, industrial and domestic pollution, landfill, quarrying, volcanic eruptions and plankton blooms, so the visibility is less. Water clarity is better over deep water or a solid bottom. Ebb tides lower water clarity by carrying sediment off beaches and reefs; visibility usually improves on a flood tide. Care with buoyancy will prevent divers from disturbing the bottom sediment.

Heavy rain and wind reduce visibility if bad weather causes freshwater and saltwater to mix or if it sets off a plankton bloom. Offshore waters appear blue, but the decaying organic matter in coastal waters is yellow, so some of the blue is filtered out and the waters look green. Local mineral deposits or mining are also factors that can affect the colour of the water.

REPETITIVE DIVES

For surface intervals greater than 16 hours, divers can assume that there is no excess nitrogen remaining and can therefore treat the next dive as if it were the first. A second dive in less than a 16-hour period must be classed as a repetitive dive. The possible depths and times can be calculated from a dive planner, dive tables or shown by a diving computer. Divers performing repetitive dives over several days should take a complete day off after four days to allow the nitrogen remaining in the body tissues to dissipate completely.

Wrecks are perfect sheltering places for shoals of tiny fry and larger juvenile fish. This is the wreck of the Nebo at Aliwal Shoal.

DECOMPRESSION DIVES

Decompression dives are not recommended for recreational divers and most American recreational dive planners do not allow for them, although European dive tables do. There may be times when, for whatever reason, divers exceed the no-stop dive time limit at a given depth and then have to make stops on the ascent, long enough to let excess nitrogen diffuse out of their body tissues (decompression stops).

Different training agencies recommend different depths and times for these stops, though the deeper ones are more easily maintained in a swell. If the divers have not been very deep and not for too long, then one stop will be sufficient, usually at a depth of between 3m (10ft) and 6m (20ft). If the divers have been relatively deep or exceeded the no-stop time for longer, they will have to make additional stops at greater depths and then a longer one between 3m (10ft) and 6m (20ft). Special tables are available for diving at altitude or on Enriched Air Nitrox.

FINISHING A DIVE

Divers should finish all dives, whether decompression or not, with a five-minute safety stop at 3-6m (10-20ft). It can be difficult to hold a stop at 3m (10ft) in a swell. It is easier to hold 5m (16ft), which allows leeway if the swell causes you to ascend a little.

ALTITUDE AND FLYING AFTER DIVING

When diving at altitude, divers must use tables or computers designed for altitude diving. The reduced pressure in aeroplanes at height can cause large bubbles to form, causing decompression sickness in divers who fly before their body has had enough time to release most of the accumulated nitrogen. Even worse, high-flying aircraft cabins have been known to depressurize in flight. Divers intending to fly should allow at least 24 hours after diving.

CLIMATE CHANGE

Scientists disagree over the rate and likely extent of change resulting from global warming. Similar events have occurred throughout history and some glaciers are currently expanding. In Antarctica the Ross Ice Shelf has grown several kilometres (miles) in the last two decades. However, most glaciers are receding and large amounts of polar ice are melting. The resulting increase in sea levels threatens the existence of low-lying islands such as the Maldives and increases the risk of flooding on the lower sides of regions such as the UK.

THE EL NIÑO-SOUTHERN OSCILLATION PHENOMENON (ENSO) AND LA NIÑA

El Niño conditions can result in strange weather patterns in some diving areas. Warm water means that many sharks descend to deeper, colder water, but most importantly, animals that have symbiotic algae may expel them as in coral bleaching.

In normal years, the upwelling cold water in the trade-wind belts off the west coast of South America leads to rich fishing and causes the overlying air to cool below the temperature at which water vapour condenses (dew point), producing fog. However, sea-surface temperature changes in the equatorial Pacific sometimes produce a major climatic disturbance known as El Niño, Spanish for The Boy Child, because Peruvian fishermen noticed that it often began around Christmas. During an El Niño/Southern Oscillation Phenomenon, a weakening of the easterly trade winds in the Central Pacific means that warm surface water is no longer pushed west to allow for a cold, nutrient-rich upwelling off the coasts of Peru and Ecuador. The warmer sea-surface temperature transforms the coastal climate from arid to wet and causes the huge fish stocks, normally associated with the nutrient-rich cold water, to migrate away. The phenomenon is normally accompanied by a change in atmospheric circulation, called the Southern Oscillation. It is associated with changes in precipitation in regions of North America, Africa, and the western Pacific, droughts and bush fires in Australia and droughts in southeastern Asia, India and southern Africa. It is one of the main causes of change in the world’s climate, and the 1997/8 event was the worst on record. The sea-surface temperatures in most tropical seas were particularly high, resulting in large-scale coral bleaching, particularly in Bahrain and the Maldives. Nearly every region on earth felt El Niño’s effect in some way.

BLEACHING

Bleaching occurs when corals, anemones, clams and some other animals like sponges, expel their symbiotic algae (zooxanthellae) or the pigments of those algae. This is thought to occur due to higher temperatures and excess ultraviolet light penetration due to failed monsoons, very calm seas or lack of cloud cover. Some bleaching may be a seasonal event in the Indo-Pacific and the Caribbean, when full recovery is normal. If the water temperatures quickly return to normal then the animals recover, otherwise they die. Bleaching is most pronounced in water less than 15m (50ft) deep and particularly affects fast-growing species such as Acropora. Slower growing massive species like Porites also bleach, but are more likely to recover in a couple of months.

Bleaching was particularly far-reaching during the 1997/8 El Niño-Southern Oscillation Phenomenon, with areas such as Bahrain, the Maldives, Sri Lanka, Singapore, and parts of Madagascar and Tanzania being seriously affected. Scientists recently found that after having expelled one type of Zooxanthellae, some corals can take up other types that are better suited to the higher temperatures, thus enabling them to survive as long as temperatures do not get too high.

El Niño is called a warm event. La Niña, which means The Little Girl is called a cold event. (The phenomenon is also known as Viejo, the Spanish word for old.) The opposite of El Niño, with unusually cold surface temperatures in the Eastern Tropical Pacific, it usually, but not always, follows an El Niño and did so in 1998. The effects on global climate are the opposite to those of El Niño.

WEATHER, CURRENTS AND TIDES

In regions where there is a distinct summer and winter, many divers would normally avoid diving at offshore sites in winter. Some areas have distinct seasons of travelling storms of great violence that form over warm oceans when several thunderstorms release heat. These tropical cyclones are known as hurricanes in the North Atlantic and eastern North Pacific, and as typhoons in the western North Pacific. The winds of these systems revolve around a centre of low pressure, ‘the eye,’ in an anticlockwise direction in the northern hemisphere and in a clockwise direction in the southern hemisphere.

Tropical cyclones are a phenomenon of the tropical oceans. They originate in two distinct latitude zones, between 4° and 22° South and between 4° and 35° North. They are absent in the equatorial zone between 4° South and 4° North. Most tropical cyclones are spawned on the poleward side of the area known as the intertropical convergence zone (ITCZ).

Monsoon winds are primarily caused by the difference between temperatures over large landmasses and adjacent large oceans, notably Arabia, Asia, Australia, and the Indian subcontinent. Seasonal changes in temperature are large over land, but small over oceans. A monsoon wind blows from cold to warm regions and, in summer, from the sea towards land carrying humid air from the ocean. In winter it blows from the land toward the sea. As a consequence, where monsoons occur, one side of a landmass may get heavy rain and not be divable at one time of year and the opposite side of that landmass at another.

Some regions are known for consistently bad tropical cyclones or monsoons at certain times of year and the resorts shut down for that period. Regions where these events only occasionally cause problems, tend to stay open during the bad weather season, while offering cheaper rates. Divers who book resorts in these regions at this cheaper time of year should be aware that their holiday could be ruined.

Although not necessarily of tropical cyclone strength, bad weather can occur anywhere at any time of year. However, diving can be quite pleasant during inclement weather, if divers jump into the water and quickly descend below the swell. The real problems are in getting the boat out to the site and, worse, getting out of the water into a boat in a heavy swell.

MAJOR CURRENTS

Although local currents vary during the day due to winds, upwellings, downwellings and the heat of the sun, there are more consistent current patterns in the world’s oceans that affect the climate, conditions for diving and which migratory species can be found at a given time in a normal year.

Ocean currents are horizontal and vertical circulation systems of ocean waters that are produced by the earth’s rotation, gravity, wind friction, and the variations in water density that result from differences in temperature and salinity.

For instance, the currents that form the Gulf Stream bring warm waters northward, affecting the climates and waters of the Bahamas, Bermuda, eastern North America, the British Isles and the Atlantic coast of Norway. This leads to tropical species off Bermuda and some surprising species such as Ocean Sunfish and Leatherback Turtles visiting the west coast of the UK. Similarly, part of the South Equatorial Current that flows towards East Africa joins the Agulhas Current and relatively warm water flows southward at high speed along the east coast of South Africa. However, when this current is reversed, cold water flows north, bringing with it huge quantities of sardines, which in turn attract large predators.

The Lionfish (Pterois miles) is the Indian Ocean relative of the Pacific’s Pterois volitans. They are often treated as a single species.

Tube worms burrow into sediment or live coral. They retract instantly into their tubes if a shadow passes over them.

The Red Sea Bannerfish (Heniochus intermedius) is endemic to the Red Sea. Juveniles form shoals, but adults are solitary or in pairs.

TIDES

Tides are primarily caused by the combined effects of the centrifugal force of the spinning earth and gravitational attraction between the moon and the earth. The sun, despite its huge size, is so far away that its effect on the tides is only about half that of the moon. The cycle of one tide, to go from high water to low water and back to high water again, usually takes roughly 12 hours (semidiurnal). In some parts of the world it may take roughly 24 hours (diurnal), depending on whether the sun or the moon is dominant. Some areas experience a mixture of both diurnal and semidiurnal tides. The normal tidal day is 24 hours and 50 minutes. Around some islands and reefs you may, effectively, get four tides per day if the flow along one side of the obstacle is longer than along the other.

Spring tides, those of maximum range and flow, occur twice a month at, or near, a new or full moon. Equinoctial spring tides, those that are of greater than average range and flow, occur near the equinoxes in March and September, at new and full moon. Neap tides, those of minimum range and least flow, occur twice a month at or near the first and last quarters of the moon. These are best for wreck diving and photography. The word spring (an outflow of water) and the word neap (Anglo-Saxon for scanty) are both from Old English. Local tide tables enable divers to calculate incoming flood tides, (sea level rising), outflowing ebb tides (sea level falling) and slack water, the time of least flow when tides are changing from flood to ebb or vice versa.

The shape of the shoreline has an effect on the height of the tide. Where stretches of water are enclosed by a shoreline with a funnel shape, tides are amplified as the funnel narrows. The upper parts of Nova Scotia’s Bay of Fundy have the world’s highest tidal range - 16m (52ft).

THE MARINE ENVIRONMENT

Viewed from space the oceans dominate the earth, covering 70 per cent of our planet. They provide us with food, a large area for recreation and they regulate the climate. Mankind has treated the oceans as a rubbish pit for centuries. However, modern agricultural and industrial pollution is much more damaging and is accompanied by prodigious overfishing, often by detrimental methods. The combined effect has been threefold: huge plankton blooms (that suffocate organisms below), damaged reefs and depleted fish stocks. Ships taking on seawater as ballast in one region and discharging it in another, and aquariums emptying exotic fauna and flora into seas where they have no natural predators, have severely upset the ecology, often with disastrous results. We are slowly learning that there is a limit to the way in which we can treat the oceans.

Storm-driven wave action will occasionally damage coral reefs. However, some human activities, such as blast and cyanide fishing, coral mining, landfill, dredging, siltation caused by dredging or logging, and the indiscriminate collection of corals to sell as curios, are just as destructive. Similarly, overfishing depletes fish life, upsets the food chain and, in the case of herbivorous fish, leads to the corals becoming overgrown with algae. Corals found deep down in temperate waters are also being damaged by destructive fishing methods.

As diving becomes more popular, environmentalists are becoming increasingly concerned by the damage done by careless divers to live corals. Some diving operators in warm waters have banned the use of gloves, except on wrecks, in an effort to stop divers from holding on to live coral. If divers have to settle on the seabed to practise diving exercises or adjust equipment, they should do so only on dead sand to avoid killing live coral.

The growing awareness of environmental issues has given rise to ecotourism - tourism with an ecological conscience. Ecotourism is often summed up as ‘take nothing but photographs, leave nothing but footprints,’ but even footprints, as indeed any form of touching, is a problem for corals. It may be better to manage tourism, and the tourists themselves, in such a way as to be ecologically sustainable. The capital investment necessary to develop ecotourism is minimal, much-needed employment becomes available to the local population and in the long term the profits exceed those of logging or overfishing.

Although many divers, dive operators and diving resorts lead the field in protecting marine ecosystems, we all require somewhere to eat and sleep. If a small resort is built without a waste-treatment system, the nearby reefs may not be damaged irreparably. However, if those same reefs attract increasing numbers of tourists and more resorts, then controls on the resorts, visiting divers from nearby areas, and visiting live-aboard boats, become necessary.

Coral reefs are not the only places affected by divers, but that is where concentrations of divers are found. There is also concern over some divers’ behaviour in places where annual congregations of larger animals occur, but this can be controlled by educating divers and operators.

It has been suggested that in a few cases environmentalists have gone too far. If rules in one area are too strict, divers and snorkellers will lose interest in that area and either give up entirely or go elsewhere. Either way, if divers and snorkellers are not around regularly to keep an eye on the animals or coral reef, and the local people do not gain employment from tourism, there is more chance of unscrupulous fishermen wiping out the animals or using damaging fishing methods on reefs.

ECO-FRIENDLY DIVING

Ecological sustainability of the marine environment depends as much on individual divers as on dive operators and resorts.

■Do not touch living marine animals or organisms with either your body or your diving equipment.

■Control your fins. Their size and the force produced by the fin-stroke can damage large areas of coral. Do not use deep fin-strokes next to the reef, the surge of water can disturb delicate organisms.

■Master good buoyancy control. Much damage is caused by divers descending too rapidly or crashing into corals while trying to adjust their buoyancy. Be properly weighted and if you have not dived for a while, practise your skills where you can do no damage.

■Do not kick up sand. Clouds of sand settling on the reef can smother corals. Snorkellers should be careful not to kick up sand when treading water in shallow reef areas.

■Do not stand on corals. Living coral polyps are easily damaged by the slightest touch. Similarly, never pose for pictures or stand inside giant basket or barrel sponges.

■Do not collect or purchase shells, corals, sea stars, turtle shells or any other marine souvenirs.

■If you are out of control and about to collide with the reef, steady yourself with your fingertips on a part of the reef that is already dead or covered in algae. If you need to adjust your diving equipment or mask, try to do so in a sandy area away from the reef.

■On any excursion, whether with an operator or privately organized, make sure you take your garbage back for proper disposal on land.

■Take care in underwater caverns and caves. Avoid several people crowding into a cave, and do not stay too long, because your air bubbles collect in pockets under the roof of the cave and delicate creatures living there ‘suffocate’ in air.

The endearing Dusky Anemonefish or Clownfish (Amphiprion melanopus) in a Heteractus crispa anemone at Pulau Redang.

A colourful Gorgonian with its polyps retracted on the reef edge at Calusa Island in the Philippines Sulu Sea.

Close-up of a Humphead or Napoleon Wrasse (Cheilinus undulatus) at Taytay Bay, Philippines. One of the largest of reef fish.

■Before booking a dive trip on a boat, ask about the company’s environmental policy - particularly on the discharge of sewage and anchoring. Avoid boats, both live-aboard and day, that cause unnecessary anchor damage, have bad oil leaks, or discharge untreated sewage near reefs.

■Do not participate in spear-fishing for sport, selectively killing the larger fish upsets the chain of reproduction. If you are living on a boat and relying on spear-fishing for food, make sure you are familiar with all local fish and game regulations and obtain any necessary licenses.

■Do not move marine organisms around to photograph or play with them. In particular, do not hitch rides on turtles, Manta Rays or Whale Sharks, since it causes them considerable stress.

THE ETHICS OF FEEDING

Conservationists argue that feeding fish alters their natural feeding behaviour, affects their health, makes them dependent on divers and could attract more dangerous predators. They have a point with regard to feeding Humphead (Napoleon) Wrasse with eggs or any fish with food that is not part of its natural diet, but others argue that feeding does not alter long-term behaviour. Most animals are opportunistic feeders, not averse to carrion and the amount of food that divers introduce is minimal so the fish do not become reliant on it. At the Cayman Island’s Stingray City, where the rays are fed many times each day, the rays are still observed feeding naturally and at shark feeds a few dominant animals take most of the food, while most sharks present go without. More importantly, the quantity of divers these events attract, causes governments to realize that the animals are worth more when kept alive for tourism than wiped out by fishermen. It is estimated that half the diving/snorkelling dollars spent in Grand Cayman are on the stingray feeds and that in the Bahamas shark-feeds bring in over $60 million a year.

Typical view of a northern Red Sea reef. Colourful anthias forage over a mixture of soft and stony corals on Jackson Reef in the Strait of Tiran.

However, things must be placed into perspective. Sharks have attacked in areas where no feeding occurs and without obvious reason. When wearing light-coloured fins, I have had them bitten by large groupers and sharks at dive sites where no feeding had ever taken place. Possibly, the larger fish considered the fins to be smaller, prey-sized fish. A large barracuda has also attacked me in water with poor visibility. I was wielding a camera at the time so a glint of sun on the lens may have looked like the flash of a small silver fish. I know two divers who have been bitten by sharks while swimming too close to bait-balls that the sharks were feeding on. Several well-known operators have been badly bitten by groupers or moray eels that they fed regularly, but at the time of the respective incidents they were feeding another fish. Several people have suffered small grazes at organized shark feeds in the Bahamas.

Even where hundreds of non-cage shark feeds are performed yearly with hand-feeding and/or large amounts of bait, there have been few injuries and those that did occur were mostly to those doing the hand-feeding. When sharks attack spear-fisherman, they are usually carrying dead, or worse still, struggling-while-they-die fish. Eventually, by the law of averages a tourist will suffer a serious injury or die during a feeding operation. However, the incident-rate is well within the range of adventure sports in general and much safer than mountaineering, skiing or snowboarding. Many more people are killed by bee-stings.

There are many locations where fish feeding is restricted or prohibited. Recently the anti-feeding lobby in Florida, backed by spear-fishermen and commercial fishermen, managed to have fish-feeding banned. Media frenzy claimed that more shark attacks than usual had occurred locally, but this was not true. The rule-makers ignored the fact that currents had driven fish-shoals inshore; that people were filmed swimming among shoals of fish on which sharks were preying; and that a myriad of commercial fishermen were chumming the water, catching, killing and cleaning fish right off the tourist beaches. Florida now has a situation where dive operators are not allowed to use chumsickles (large blocks of frozen fish parts) to attract sharks, yet spear-fishermen and commercial fishermen are still permitted to use this baiting technique to attract sharks and other marine animals.

With reference to feeding sharks, some species are more belligerent than others, and Grey Reef Sharks can be more so in some areas than in others. Having regularly organized shark feeds in the Red Sea since the early 1980s, my feeling is that many operators use too much bait. A couple of 25cm (10in) fish hidden in the coral are enough to keep the sharks interested for 20 minutes. It is also better not to hand-feed, even with chain-mail gloves, as this gives the sharks the impression that man supplies the food and could result in sharks harassing divers who are not involved in feeding.

The case of researcher Erich Ritter being bitten by an adult Bull Shark at Walkers Cay, Bahamas, while being filmed for the Discovery Channel’s Shark Week series, will not help the pro-feeding lobby. However, those who regularly dive with sharks believe that if done in a responsible manner, shark dives are reasonably safe. We are privileged to have close encounters with wildlife underwater, often within arm’s length. Not everyone wants to get this close to a shark, but there have been many instances where other animals such as large barracuda, large groupers, Moray Eels and even Titan (Moustache) or Yellowmargin Triggerfish have either bitten or butted divers in situations not connected to feeding. Feeding fish is an emotive issue - you will have to make up your own mind.

DIVING WITH GASES OTHER THAN NORMAL AIR

ENRICHED AIR NITROX

The term Nitrox is commonly applied to oxygen-enriched air. By increasing the percentage of oxygen, and thus decreasing the percentage of nitrogen, divers will absorb less nitrogen during a dive and have less to eliminate during the ascent.

Diving on Nitrox can be treated in several ways. By calculating dive-plans from Nitrox tables, divers will have longer no-decompression stop times at their maximum depth. If calculating dive-plans from air tables, they will have an extra safety factor. If divers go into decompression, it will be shorter if calculated from Nitrox tables, but have a greater safety factor if calculated from air tables. Many divers feel less fatigued after diving on Enriched Air Nitrox, though there is no scientific proof of this, and many experience a lower rate of gas consumption.

Another way in which Nitrox can be used to divers’ advantage is that divers, who have been deep while breathing air or other gas mixtures, can shorten their decompression times at shallow depths by changing to a mixture containing 50-80 per cent oxygen. This mixture enables faster elimination of excess nitrogen (if using air) or helium (if using mixed gases). However, due to oxygen toxicity, the depths to which divers can descend depend on the percentage of oxygen in the Nitrox mix used. The higher the percentage of oxygen, the shallower will be the maximum depth to which they can go. Divers should not descend to depths where the partial pressure of oxygen exceeds 1.4ata. Atmospheres absolute (ata) is the sum of atmospheric pressure and the hydrostatic pressure - the total weight of water and air above us.

There may be circumstances when a diver breathing Enriched Air Nitrox has to go deeper than oxygen toxicity allows on that particular Nitrox mixture. In this situation, if the diver has a separate small cylinder of normal air fitted with its own regulator, it is possible to switch to breathing from this cylinder for a brief foray deeper than the depth allowed on the Nitrox mixture. The diver can then switch back to breathing Enriched Air Nitrox after returning to a depth where oxygen toxicity is no longer a problem.

Another problem with oxygen breathed at higher than normal partial pressures, is that when used over long periods it affects the central nervous system. Divers must be careful not to exceed the recommended oxygen tolerance units (OTUs), particularly on repetitive dives.

High concentrations of oxygen cause combustion on contact with oils and greases. Scuba cylinders and their valves come in contact with pure oxygen during filling, so they must be scrupulously clean. Standard regulators should be suitable for Nitrox mixtures of less than 40 per cent oxygen, but for higher concentrations, their O-rings must be replaced with ones that do not require lubricants.

HELIOX AND TRIMIX

For deeper diving, one must lower the oxygen content to reduce oxygen toxicity as well as reducing the nitrogen content. This is done by replacing some of the nitrogen with helium (Trimix) or all the nitrogen with helium (Heliox). Helium has the advantage of reducing problems with Nitrogen Narcosis, but gives no advantage with decompression times. It is a lighter element than nitrogen and more of it is absorbed by the body, which then has to be eliminated on ascent. It also conducts heat away from the body more quickly during respiration.

As divers go deeper they must reduce the oxygen content still further. There is almost an optimum mix for each depth. Divers use a ‘travel-mix’ suitable for breathing from the surface down to a calculated depth and then switch over to a ‘bottom-mix’ with an even lower oxygen content. However, bottom-mixes have too low an oxygen content to be breathed safely at shallower depths. During ascent, there will be a depth at which the divers must switch back to the travel-mix; shallow decompression stops will be shorter if they switch to mixes high in oxygen when close to the surface. Deep dives using Heliox or Trimix involve several clearly-marked cylinders of different gas mixtures and the diver has to identify the correct regulator attached to the correct cylinder, for each phase of the dive. This has led to the development of modern rebreathers, in which the gas mixture can be modified as one changes depth.

Divers pass the entrance of a cavern in the Amirantes in the Indian Ocean. Black corals are often found in the dim light under overhangs.

REBREATHERS

The acronym SCUBA stands for Self-Contained Underwater Breathing Apparatus. With traditional SCUBA we waste most of the oxygen we breathe by exhaling into the water. This is termed an open-circuit system. Some companies have modernized, closed or semi-closed circuit scuba equipment for recreational use and these are termed rebreathers. When using rebreathers, divers breathe a gas mixture containing oxygen and when they exhale, the carbon dioxide in their exhaled gases is chemically removed by passing the gases through Soda-Lime. The Soda-Lime is referred to as a scrubber. Some additional oxygen is added to the cleaned, exhaled gases and that mixture is breathed again, hence the name rebreather. The closed-circuit system does not dump any gas into the water until the diver ascends, while the semi-closed circuit system only dumps a small portion of each exhalation. In this way divers get long diving times out of a relatively small amount of breathing gas.

Rebreathers can be based on Nitrox or, for deeper diving, Trimix or Heliox. They require considerable maintenance and a constant eye must be kept on gauges to ensure that everything is working correctly.

TRAVELLING TO DIVE

The terrorist attacks on the USA of 11 September 2001 mean that the security for air travel will never be the same again, with underwater photographers and divers being the hardest hit. Many airlines now have strict rules and limits on checked and carry-on baggage.

Apart from the necessary paperwork, passport, visa, vaccinations/health certificates, travel and diving insurance, necessary prescription medications and ‘C’-card, the most important part of travelling to dive is to have these and other essentials such as cameras, film or memory cards, diving computers, prescription masks and spectacles in your carry-on baggage. Flights are notorious for losing or delaying baggage.

Your passport should be valid for six months longer than the expected duration of the trip and have at least six empty pages. If you carry local banknotes, these should be clean and unmarked. Have photocopies of all paperwork, passport photographs for local permits and your driving license if intending to hire a vehicle.

Keeping diving equipment within most airlines’ check-in baggage limit of 20kg (44 lb) is a problem. Some airlines will allow an extra 10kg (22 lb) for divers on presentation of a C-card. American airlines have more sensible baggage limits based on size.

DIVE PLANNING - ‘PLAN THE DIVE AND DIVE THE PLAN’

All dives should be planned. The leader of the dive should give a detailed briefing that covers the expected time in the water, what the current is doing, what should be seen on the dive, what depth divers should expect to dive to and when they should ascend.

However, divers should also take into account their own health and fitness, and normal rate of air consumption. They should consider the depths and times of their last few dives, the surface intervals between them and the time that has elapsed since the last dive. There is now some debate over whether the first dive of the day should always be the deepest and all other dives on the same day progressively shallower, but it is best to keep to the standard practice.

Diving bags or rucksacks are preferred for easy stowage by live-aboard boat skippers, but they attract attention as containing expensive equipment and do not stand up well to airport baggage handlers. Pelican cases are also prime targets for airport thieves. Shabby cases are a better option.

Check out what equipment is available for rent at your destination so that you can minimize your checked baggage. However, remember that at Third World destinations rental equipment may be in poor condition and fins and wet suits are often too small for large Caucasians.

TRAVELLING DIVER’S CHECK LIST

■Clothes and wash kit for surface use

■Mask, snorkel and fins (either full-foot or adjustable with bootees)

■Regulator with contents gauge (manometer) and alternate air supply

■Buoyancy Compensator Device (stabilizing jacket)

■Weight belt and weights if not provided by the operator

■Compass

■Diving knife and shears for cutting monofilament line (some airlines no longer allow diving knives to be carried even in checked baggage)

■Diving computer, preferably with watch, depth gauge and tables

■Wet suit, Lycra skin or dry suit

■Delayed deployment or other surface marker buoy or flag

■Whistle or powered whistle

■An old CD for use as a heliograph

■Waterproof light

■Diving log book

■Mask anti-misting solution (liquid detergent works just as well!)

■Slate and pencil or other form of underwater communication

■Swimming costume and sunglasses

■Spare prescription spectacles if worn

■Wet bag for diving gear

■Dry bag or case for paperwork, cameras, medications, wash kit etc.

■First aid kit

■Towel if not supplied at destination

SPARES KIT

■Mask and mask straps, fin straps and knife straps

■O-rings, including a few for cylinder/regulator fitting

■Any necessary tools for small repairs, and batteries

Regulators travel best when disassembled, and you may need special tools to re-assemble them. Diving computers and depth gauges should travel as hand baggage on aircraft or in a pressure-proof container.

TRAVELLING DIVER’S MEDICATIONS

A minor ear or sinus infection can ruin a diving holiday, especially in a remote area or on a live-aboard boat. Being prepared can save your vacation. Many divers travelling to a live-aboard boat assume that they do not require antimalarial prophylactics because they will spend most of their time at sea where mosquitoes do not exist. However, it only needs one mosquito bite in an airport and there is always the chance of aircraft or boats being delayed, forcing extra time at risk on land.

The correct malaria prophylactic should be taken where necessary and most divers carry decongestants, drops that dry out the ears, antihistamine cream, sunburn lotion, lip-salve, anti-diarrhoea medicine, rehydration salts, antibiotics, seasickness remedies and insect repellents.

Masks that keep ears dry are now available.

Remember that most decongestants and seasickness remedies can make you drowsy and should not be taken before diving.

Squirrelfish (Sargocentron Spp) of different species form loose aggregations in protective crevices during the day and feed at night.

Whale watching has become a popular pastime in the Atlantic, often bringing in a considerable income from tourism. Whales are identified by markings and scars on their tails.

A pair of Clown Anemonefish (Amphiprion percula) among the tentacles of their host anemone. Sulawesi, Indonesia.

Cleaner shrimp on anemone, Caribbean.

The Red-tipped Sea Star (Fromia monilis) is one of the commonest species of Fromia in the western Pacific and one of the most striking.