Shark's do not have bones. A shark's skeleton is made of cartilage.

Sharks breath though five to seven openings call GILL SLITS on each side of their heads.

Sharks can not hover because they do not have a SWIM BLADDER, a balloonlike organ than helps fish float. Sharks must keep swimming or sink to the bottom.

A shark's brain is very small, only three to six inches long. Most of their brain is devoted to their senses. Sharks can smell one drop of blood in one hundred million drops of water.

Reference
Pearce, W. (1987) Sharks - Amazing Facts Activity Fun Book, Playmore Inc: New York.

Links to Sharks
Shark Attack
Zoom Shark