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The seven principle marine predators are:

moray eels
large grouper
sea snakes
salt water crocodiles
killer whales

Actual attacks and fatalities are rare, and occur when a diver is mistaken as a food source or intrudes into the creature's territory.

Great Barracuda
Barracudas are usually found in warm, tropical regions; some also in more temperate areas. They are swift and powerful, small scaled, slender in form, with two well-separated dorsal fins, a jutting lower jaw, and a large mouth with many sharp large teeth. Size varies from rather small to as large as 4-6 feet (1.2-1.8 meters) in the great barracuda (Sphyraena barracuda) of the Atlantic, Caribbean, and the Pacific.

Barracudas are primarily fish eaters of smaller fishes, such as mullets, anchovies, and grunts. They are good, fighting sporting fishes, and the smaller ones make good eating. In certain seas, however, lately increasingly they may become impregnated with a toxic substance that produces a form of poisoning known as ciguatera.

More about barracudas here.


Moray eels occur in all tropical and subtropical seas. They live in shallow water among reefs and rocks and hide in crevices. They differ from other eels in having small rounded gill openings and in generally lacking pectoral fins. Their skin is thick, smooth, and scaleless, while the mouth is wide and the jaws are equipped with strong, sharp teeth, which enable them to seize and hold their prey (chiefly other fishes) but also to inflict serious wounds on their enemies, including humans. They are apt to attack humans only when disturbed, but then they can be quite vicious.

They injure you with their razor sharp teeth and powerful jaws that can lock. Injuries can result in bleeding, severe muscle damage - also chipped bones. Stop any bleeding, clean wounds thoroughly. Get medical help to guard against infection.

More about
moray eels here.

Large Grouper
Grouper have several sets of teeth, placed in the mouth to act as raspers or holding teeth. The fish gulps down its prey using these raspers to prevent the smaller fish from escaping. The teeth are not used to tear or slash, as with barracuda or sharks.

The jewfish is a member of the grouper family and some can get as large as 800 pounds, and can easily endanger a human, although I know of no reports. This fish is totally protected in Florida waters.

More about large groupers here.

Sea Snakes

Sea snakes are air breathers probably descended from a family of Australian land snakes. They inhabit the tropical waters of the Indo-Pacific and are highly venomous. Thirty-two species have been identified in the waters about the Barrier Reef in Australia.

More about sea snakes here.

Saltwater Crocodile

This endangered reptile actually is a danger to underwater enthusiasts and a number of people are killed and injured each year. It's hide has a very high commercial value because of its ease of skinning and because of this it is protected.

More about saltwater crocodiles here.