necto-, nect-, nekto-, nek- +

An organisms attached to actively swimming (nektonic) forms: Epinektons adhere to animals in a body of water, but are themselves incapable of independent movement against water currents.

Concerning a creature that is fixed to an animal actively swimming: Epinektonic organisms can be seen attached to ocean animals that can move around in the water independently.

An organism that spends its lifespan swimming: Many ocean fish can be termed to be holonektons because they can only survive in saltwater of the seas.

A living thing that swims in fresh water: Some creatures that can glide through ponds or marshes can be called limnonektons.

A partial swimmer or one that passes only part of its life-cycle swimming: Some water creatures are meronekons because they don't spend their whole life swimming in water.

Swimming by means of cilia: Some unicellular organisms can move freely by nectism in which they make lashing movements with their hairlike projections in order to propel themselves forward.

An organism that swims actively just above the bottom of the sea, a lake, or another body of water: Jack was able to see the small nectobenthos swirling around at the lowest part of the stream close to his home.

1. One of the zooids of certain Siphonophora having the relative shape and the essential structure of the bell of a jellyfish: The nectocalyx uses its form and body structure as a swimming organ.
2. The swimming bell or umbrella of a jellyfish of medusa; nectophore: When Sammy was standing close to the side of the harbor, he could see the nectocalyx of the Portuguese man-of-war floating close to the surface.
3. A modified medusiform adapted for swimming purposes found as part of a siphonophore colony: In the science book James was reading, a nectocalyx was described in regards to its movements in water.

A free-swimming larva in some polychaetes: Nectochaetae have 3 to 13 segments and are hence metatroch larvae, and each segment has a pair of bristled appendages called parapodia.

The cavity (used for swimming) of a nectocalyx: A nectocyst or nectosac is the interior of the swimming-bell or nectocalyx of a jellyfish.

A free-swimming form of certain parasitic or promastigote flagella: In her science class at school, Susan had to use good reference books to find out more about nectomonads for her term paper.

Consisting of marine hairworms with a parasitic stage in various crustaceans: Nectonematoidea have a double row of natatory bristles used in swimming, and an expansive pseudocoel, a body cavity which is not a normal stomach.

A long slender sea worm (hairworm) with short bristles along either side for swimming: The larvae of the nectoneme of the genus Nectonema live as parasites on crabs and related crustaceans.

The swimming bell of a siphonophore: The hydrozoans are transparent marine organisms that can swim or float using the nectophores.

In zoology, a swimming organ or a limb (as of a mollusk) adapted for swimming: The nectopods are appendages that some invertebrates with a soft unsegmented body, such as squids, use for swimming.