Sharks lack the gas bladder that allows bony fish to control their buoyancy precisely, for example, and instead have to rely on swimming, buoyant fatty livers and, occasionally, a gulp of air.

• 比如鲨鱼没有硬骨鱼类用来精确地控制浮力的气体膀胱，但是它可以依靠游泳技术和有浮力的蓬松的肝脏来控制浮力，只需不是浮上水面吸上一口空气。