Creature Teacher:
DIVING IN THE COMPANY OF SHARKS

Be prepared. Learn what kinds of sharks you are likely to encounter in the area in which you plan to dive and know something of what to expect of each species' behavior. Bear in mind that maintaining diver safety becomes significantly more difficult with decreasing visibility (such as at night or in turbid water) and with increasing depth, current, task loading (such as carrying an underwater camera, speargun, or other equipment) and number of sharks. Never allow yourself to forget that the ocean itself is far more dangerous than any shark. Know your own limitations, and dive within them. Discuss dive logistics and contingency plans (hand signals, site analysis, entry and exit considerations, separation procedures, etc.) with your dive buddy before you enter the water.

A chance encounter with a shark in the wild is one of the most thrilling of underwater experiences.  But the presence of bait and -- especially -- bait with competing sharks changes the nature of the encounter dramatically.  The Silvertip Shark (Carcharhinus albimarginatus) is generally unafraid of divers in unbaited contexts, but becomes quite belligerent and even 'snappy' when bait and competing sharks are present.

Oceanic Whitetip Shark (Carcharhinus longimanus)

While diving, try to behave like a well-mannered 'guest' - remember that you are a visitor in the shark's living room. Let any shark you encounter approach and investigate you on its own terms. Do not chase, corner, grab, knife, spear, or touch the shark in any way; it is a wild animal that will defend itself if it perceives itself to be threatened (though in all likelihood, if you do behave in a way that seems threatening to it, the shark will simply swim away, rather than snap at or bite you - but it's best to not take that chance or otherwise force the issue).

Try to avoid staring directly at the shark. Sharks are very aware of a diver's eyes and seem to dislike being stared at as much as you or I do. Instead, watch it from 'the corner of your eyes'. For your own safety, however, it is important that you do not loose sight of the shark while it is in your immediate vicinity. Remain vigilant for several minutes after the shark has apparently left, to be sure that it has, in fact, gone.

During your encounter with a shark, remain motionless - preferably on or near the bottom (try to become an unthreatening 'part' of the natural bottom topography); large or rapid movement on the part of a diver often frightens a shark into fleeing and may startle it into defensive attack.

Reduce your vertical profile in the water; crouch down on or near the bottom or orient yourself horizontally in the water column (sharks often seem more unnerved by height than length - perhaps because the vast majority of creatures it encounters are longest horizontally, in the direction of travel).

Avoid clustering with other divers (sharks often seem to perceive tightly packed groups of divers as a single, large, and altogether frightening super-organism). Remain close enough to your buddy to maintain safety, but relatively far away from other such buddy pairs. Leave solo diving with sharks to the professionals.

To prolong your encounter, take advantage of the shark's natural curiosity. Try humming quietly into your regulator (almost any tune with a simple but not-too-regular rhythm works pretty well). Or try clinking two rocks together or clanging the butt of your dive knife against your scuba tank - these simple techniques are sometimes quite successful in luring a curious shark closer to investigate. If you have a brightly-colored camera housing or reef gloves, they may also help pique a shark's curiosity - but do not attempt to gesture while wearing such gloves: they may look edible to a shark.

Do not use bait or otherwise attempt to feed a shark while underwater. Feeding contexts radically change the character of a shark's investigative behavior, and may lure other sharks, adding a competitive 'wild card' factor to the mix. Under such conditions, a shark encounter can change from wonderful and serene to downright dangerous in a fraction of a heartbeat. Leave shark feeding and working with baited sharks to the professionals.

If you must surface while a shark is in your immediate vicinity - due, for example, to low air supply: move slowly and deliberately, never loosing sight of the shark. Swim directly to your pre-planned exit site. Avoid a long surface swim, which is tiring and may leave you vulnerable to attack from below; when you arrive at your exit point (boat, dock, beach, whatever), do not dawdle - exit the water smoothly but efficiently. (Incidentally, if you spot a shark from the surface and choose to dive with it, enter the water quietly, using a controlled seated entry rather than a giant stride entry - not only are you less likely to frighten away any nearby shark, but  sharks react with great excitement to the commotion caused by such a spectacular, noisy entry; in an excited state, a shark can become dangerous in an instant.)

Great Hammerhead (Sphyrna mokarran)

Observe the behavior of the shark very carefully. If it appears excited or agitated (quick, jerky movements; pectoral fins held stiffly downward; abrupt change in swimming style; overall increase in muscular tension) or otherwise begins to swim in an erratic manner, leave the water immediately (following the guidelines outlined above); in all likelihood, by increasing the distance between you and the shark, it will relax somewhat and either make good its escape or return to its former, more languid cruising style. It may be relatively safe to remain in the water after that, but prudence dictates a slow but efficient exit from the water (again, following the guidelines above).

Be aware of the behavior of fishes and other creatures in the immediate area: if they suddenly dive for cover, appear to behave erratically or in an agitated manner, leave the water immediately (following the basic guidelines outlined above). Trust your diver instincts - if something just doesn't 'feel' right about the situation, leave the water immediately.

Above all, enjoy the experience. You will almost certainly remember the encounter long after the shark has forgotten you.

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Behaviour: Right Whales are, despite their massive bulk, incredibly active cetaceans, with breaching, lob-tailling and flipper-slapping all relatively common. A particular favourite is 'sailing', where the whale hangs vertically upside-down in the water, 'standing' on its head, with its tail flukes in the air. They communicate through 'moans' and 'burping' noises.

Bottlenose Dolphins are found in all cold temperate to tropical seas worldwide. They occur quite regularly in coastal waters, and some populations even migrate in response to changing environmental conditions.

Classification:
All Bottlenose Dolphins are classified as Tursiops truncatus, which is derived from the Latin and Greek words for 'porpoise' and 'face'. Though there are a number of external differences between populations from various parts of the globe, no subspecies are currently recognised, and any such differences are thought to be because of varying environmental conditions.

Local Names:
Grey Dolphin; Black Dolphin; Bottlenose Porpoise; Cowfish; Bottle-Nosed Dolphin; Atlantic Bottlenose Dolphin; Pacific Bottlenose Dolphin.

Description:
The Bottlenose Dolphin is a large, robust animal with a slightly hooked broad dorsal fin. Size and some physical characteristics vary according to the distribution of each individual. In smaller forms, the well-known bottle-shaped beak is shorter and slender. It broadens as the body size increases. In some populations the melon is more rounded. Body colour also varies; the dorsal cape ranges from dark blue to brown-grey, fading to a pale grey along the flanks. The ventral surface is white-pink, and the tip of the snout is normally white. Tail flukes and the flippers' edges are grey-black. Dark lines from melon to eye and eye to flipper can also be seen. Some populations are spotted, or a dark grey-black.

The Bottlenose Dolphin measures between 1.9m and 4m, weighing 90-650kg. 

Recognition at sea:
The Bottlenose Dolphin cannot really be confused with other species - for instance, the spotted variety is more bulky in appearance than other mottled species, such as the Pantropical and Atlantic Spotted Dolphins. The broad dorsal cape and shorter snout should discern this animal from the Rough-Toothed Dolphin, which has a more cone-shaped head. In coastal waters, the size and shape of the dorsal fin should be enough to distinguish between the Bottlenose Dolphin and other local species, such as the Tuxuci, which has a more triangular fin.

Habitat:
Bottlenose Dolphins are both a coastal and oceanic species, with the former preferring waters of less than 30m in depth. The habitats they occupy is diverse, ranging from rocky reefs to calm lagoons and open waters. 

Food & Feeding:
Bottlenose Dolphins tend to prefer shoaling and bottom-dwelling species, feasting upon a wide variety of fish, squid and octopi. Cuttlefish are also taken.

Behaviour:
Bottlenose Dolphins have been reported individually, in groups of between 10-100 inshore and units of several hundred offshore. They are powerful swimmers and acrobatic in nature, often bowriding and leaping alongside vessels.

Longevity: At least 30 years (approximately).

Estimated Current Population: Unknown, but locally common.

Scientific Name: Balistoides Conspicullum 

This is one of the most ferocious of all triggerfish, capable of eating many fish smaller than itself and also of eating parts bitten off of any larger fish it can corner. This triggerfish has teeth, which are capable of doing as much damage as the infamous piranha fish of South America. The vivid and contrasting markings on it's body warn larger predators that it is harmful to eat and so aid this fish in protecting itself from any danger. This colourful triggerfish is appropriately named the clown triggerfish and grows up to 30 cm in length.

Also known as the big spotted triggerfish, it inhabits outer reef areas and feeds upon crustaceans and mollusks by crushing them with powerful teeth. They are voracious eaters, and divers report seeing the clown triggerfish devour beds of pearl oysters.

This species of trigger is common around the reefs of the Indo-Pacific and East Africa to Somoa in warm tropical coastal waters, generally near shore in relatively shallow water These colourful fish hide in crevices when in danger. A sharp spine on the back of the triggerfish locks into place and the fish cannot be pulled from the crevice. The triggerfish takes its name from the  locking mechanism of the stout first dorsal-fin spine and the smaller, slender second spine (the trigger).  When the first spine is erected, the second spine is also pulled up and functions like a cam to wedge the larger spine in a vertical position. The first spine cannot be folded down, until the tip of the second spine is pulled posteriorly.  The family name Balistidae is formed from the genus name Balistes, which is derived from the Latin ballista, another name for the Roman catapult, in allusion to the trigger mechanism of the dorsal-fin spines.  

When it comes time for spawning, most triggerfish dig a shallow crater in the sand, where the female deposits the eggs.  Both sexes have been reported guarding the nest until the eggs hatch and the larvae float away.  Should you see a trigger circling a spot on the sand, chasing other fishes that approach this location and blowing jets of water at the spot, it is likely that the fish is guarding a nest there.  Steer well clear of these nest guarders, as they are particularly aggressive, and have no hesitation in attacking and biting divers.

Do not eat this fish. According to an 1878 account, "the poisonous flesh acts primarily upon the nervous tissue of the stomach, occasioning violent spasms of that organ, and shortly afterwards all the muscles of the body. The frame becomes rocked with spasms, the tongue thickened, the eye fixed, breathing laborious, and the patient expires in a paroxysm of extreme suffering."