Different animals have different shapes underwater

some animals, like sharks and dolphins have a sleek torpedo shape, but other animals like plankton can be round or odd shaped. What drives the shape of animals underwater?

In this video we will explore the the forces acting on animals moving through an aquatic environment.

The movement of water is the result of both inertial and viscous forces. At very small body sizes viscous forces dominate, so the water feels like honey, and streamlining the body would be without value. At larger body sizes inertial forces are more important, the flow of water becomes more disordered, creating more drag. At these larger body sizes, becoming streamlined is important to reduce this drag.