. Glossary 404 Further resources 407 Pictur e credits 408 INTRODUCING AQUATIC LIFE Exploring the World of Aquatic Life L ife originated in the prehistoric seas some 4,000 million years ago. The watery. under the cover of darkness.This gives the transparent eggs several hours of relative safety away from the eyes of predators, during which they are carried away by the ocean currents .The eggs then hatch. made of a tough, elastic material called cartilage, except for the jaw. Cartilage is also found in the skeletons of another large group of primitive fish: the sharks and their relatives, the rays. What