What about attacks from Barracuda, Sharks, Moray Eels etc

The typical aquatic animal responds to human approach with "Run away! Run away!" The vast majority are timid and harmless, yet fascinating and enjoyable to watch. But there are a few that require caution. Nearly all injuries involving aquatic life (plants or animals) result from human carelessness, and the vast majority are minor. It takes only a little bit of understanding and care to avoid potential problems. You're far more likely to suffer from an unpleasant encounter with an un-aggressive organism - such as a puncture wound from sea urchins, a sting from jellyfish and their relatives, or cuts and scrapes from barnacles and coral. To avoid these, watch what you touch and wear an exposure suit as protection from accidental contact. If you're not familiar with an organism, leave it alone. An excellent rule of thumb: If it's very pretty, very ugly, or it doesn't flee from you - don't touch it! Venomous fish and other stinging aquatic animals tend to have these characteristics. Very few aquatic animals are outwardly aggressive. While it's true that almost any good sized animal is potentially dangerous when provoked, it's actually very rare for humans to suffer attacks from aquatic animals. The reputation of some animals as bloodthirsty killers, such as sharks and killer whales, resulted from inaccurate and distorted reports that become myths. The films Jaws was not based on a true story! The vast majority of incidents between sharks and divers involve spear-fishing (wounded fish stimulate shark feeding behaviour). Killer whales (more accurately, Orcas) have the capacity to harm humans, yet there's no documented case of one ever attacking a diver. Injuries from animals that may seem aggressive, such as eels and stingrays actually result from frightening animals, causing them to react defensively - such as if you carelessly stick your hand in an eels hole without looking first. (If a giant arm came in your front door and started groping around your living room, you'd bite it, too.)

So if you see a shark, or some other potentially aggressive animal, remain still and calm on the bottom. Do not swim toward it, which would trigger a defensive reaction. Watch it and see what it does. Chances are, it's just passing through. And enjoy the experience - these are some of the most magnificent of nature's creatures, and you don't get to see them too often. If it stays in the area calmly swim away along the bottom, keeping an eye on it and exit the water.