Nekton

Nekton is the grouping of organisms that live in the water column of the ocean and freshwater lakes. Nekton organisms can propel themselves independent of the currents in the water mass. Some examples are krill, small fishes, whales, and tuna, the latter two capable of substantial migrations. By contrast, those organisms that drift passively with the current (although still capable of independent movement) are grouped with the plankton.

One characteristic of nekton is the capability of fast motion.