Seawater is slightly more viscous than fresh water. Moving in Air, Moving in Water Water s viscosity has a profound effect on locomotion for smaller organisms like protozoa. These organisms must overcome viscous drag, but they must also rely on viscosity to provide their thrust. The Microscopic Movement exhibit explores how these tiny aquatic organisms get around. All living things live in a fluid, either air or water.
Air is a gas and has no defined shape and no defined volume.
Water, a liquid, has a defined volume but no defined shape. The physical characteristic that unifies gases and liquids is viscosity, their resistance to the rate of deformation. To reduce the friction of forward motion, most aquatic animals have streamlined bodies shaped roughly like a football. This body shape poses a minimum amount of resistance as water flows over it. You can tell a lot about a fish s habitat by the shape of its body.