Swimming, floating, sinking

The phenomenon of floating occurs when the dipped body and the liquid substance have the same density. The body is moving in the liquid substance neither downwards nor upwards without external impact. The volume of the body equals the volume of the displaced liquid substance. Similar to swimming, the weight force equals the lifting force.

Thanks to their swim bladder (cf. picture on the left), fishes can either increase or decrase the volume of their body - according to their needs - by filling their swim bladder with more or less gas. In this way they change their density according to the water depth. Thus they are very successful in floating effort-savingly in the water.