Nekton

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Nekton is the grouping of living 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 adult krill, small fish, 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. Most (but not all) planktonic organisms are small (greatest diameter under 1 centimeter), while nekton lengths range from a few centimeters to 30 meters. One characteristic of nekton is the capability of fast motion. Another is maneuverability, as in linear and angular acceleration, starting, stopping, turning, and in general displaying agility. The size and speed ranges of plankton and nekton mean that while plankton experience water as a viscous medium, often with reversible flows, the world of nekton is dominated by inertia (sustained vortices, coasting, etc.).

Oceanic Nekton: There are three types of oceanic nekton: Chordates are the largest and are made up of either bones or cartilage. Molluscans are animals like octupi and squids. Arthropods are animals like shrimp.

The term "nekton" was coined in 1890 by Ernst Haeckel; it is rooted in the Greek word nēktón ("the swimming"). The study of swimming organisms (biofluidynamics, biomechanics, functional morphology of fluid locomotion, locomotor physiology) is called Nektology. One who studies swimming in all its forms is called a Nektologist.