3 POINTS ON FISH

 1. Bony fish have skeletons of bone, and swim bladders to keep them afloat.

   2.  Cartilaginous  fish such as sharks, rays and ratfish, are mostly marine hunters, they have skeletons made of cartilage, and sandpaper-like skin.

    3. The primitive jawless fish have sucker-like mouths, and include lampreys and hagfish.