Marine animal attacks with serious injury to divers are uncommon. Public curiosity has generated much of the excitement created by these infrequent occurrences. Although there are approximately more than 1,000 venomous marine vertebrates, only two species of predatory marine animals that bite - sharks and crocodiles - have been responsible for confirmed fatalities. Probably the most feared marine predators are sharks, and in spite of the vast amount of fiction, few facts are available regarding the relationship of sharks to man. Most sharks are predatory, but nearly all species are too small or insufficiently armed (e.g. teeth and swimming speed) to be dangerous to man.
However, it is generally safe to assume that in the presence of blood or food, sharks bigger than four feet in length and adequately armed are potentially dangerous. From a worldwide perspective, roughly one-third of the documented shark attacks each year occur on divers. The stimulus to produce an attack by a marine animal ranges from a territorial intrusion to a feeding response. Spearfishing often provokes these attacks. Divers who participate in spearfishing are generally best advised to distance themselves from the likely source of stimulus, i.e. tethered fish or game.
Shark behavior research has shown that sharks may be attracted to the surface splashing of a swimmer or surfer, mistaking their movements for that of a sea turtle, ray or even an injured fish. With respect to "art" as a visual stimulus, there is a shark attack worthy of mention. The International Shark Attack File (ISAF), based in Gainesville, Fla., has recorded an attack on a diver in the waters of Southeast Asia, where a shark removed significant amounts of tissue from both thighs of a male swimmer. Prior to the attack, the diver had displayed two elaborate animal tattoos near the area of the wounds.
The ISAF has theorized that contributing factors for the assault suggest that the stark contrast of the skin to the colorful design of the tattoos may have attracted the shark's attention. Also, the diver may have intruded upon the territory of that particular shark. The true reason for this attack is unclear.
The barracuda family Sphyraenidae are voracious carnivores, and although there are no known reported fatalities involving the great barracuda, this fish is feared more than sharks in some areas of the world. There are some 20 different species widely distributed throughout tropical and sub-tropical waters. Often barracuda demonstrate no fear of swimmers, and they are known to be attracted to brightly colored or shiny objects, irregular motions, surface splashing and any speared or tethered fish.
From the standpoint that bright colors, in addition to contrast, may draw attention to you as a diver, diving in certain environments may pose a risk. The cautious opinion of marine animal behavior specialists is for divers to avoid behaviors and appearances which may arouse the attention of dangerous marine predators. The sea turtle is a favorite food of the shark. Another form of predator provocation comes in the form of surface splashing by swimmers or snorkelers, when the shark may mistake the movement for that of a turtle.