Some sharks are filter feeders. The basking shark and megamouth shark strain huge amounts of plankton from the water on gill rakers. Whale sharks also filter feed. They strain plankton through a spongy tissue in their mouth. Filter feeding sharks have tiny, nonfunctional teeth.
Sharks have a very streamlined shape.
This shape is good for swimming and helps keep the shark buoyant or afloat. A shark's tail or caudal fin moves them forward and downward. The side or pectoral fins provide lift much like the wings of an airplane. Also, because sharks don't have any bones they are very light in the water. And, a shark's liver stores oils and fatty acids which also provide buoyancy.