How do sharks control their buoyancy?
Since sharks lack a swim bladder, the organ that controls buoyancy in bony fish, they have very large livers containing a great deal of oil that helps them to stay buoyant. Most sharks also generally stay in constant motion which, in addition to moving water over their gill slits, also helps them stay buoyant through the physical property of lift (similar to how airplanes stay in flight by their wings) acting on their pectoral fins.
