Some parts of their skeleton, like their vertebrae, are calcified. Even the ray's skull is flattened. Rays belong to the group of fishes called Elasmobranchii, which also includes the sharks, skates, and ratfish. The Elasmobranchii are all fish that have no bones, only cartilage. They eat fish, crustaceans , mollusks , and worms.
Rays mostly hunt on or near the bottom of the ocean.
They are known to be very curious animals, often approaching a diver and simply observing the intruder. Rays live mostly on or near the sea bed. They are propelled through he water with their powerful, wing-like pectoral fins which ripple and flap. Their large pectoral fins also let them glide trough the water. Many species of rays are coated with a slimy mucous which reduces the surface tension and drag of the water and increases swimming speed.