Sharks are fish that appeared in the oceans nearly 350 million years ago, and have hardly changed at all. There are more than 350 species and only a few of them are a thereat for man. The lemon shark is a typical fish of the coral reef waters, buy the gray and bull sharks can be found in most areas of the ocean.
Sharks play an important role in the ocean's ecosystem regulating the fish population. They feed on the sick, old or wounded fish, that are not the best for reproduction. This way, only the healthy and strong ones survive having vigorous descendants that ensure the survival of the species.