Dive Atlas of the World. Jack Jackson

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,