nekton vs organism

nekton and organism both are nouns.

Word	Noun	Adjective	Verb	Adverb
nekton	Yes	No	No	No
organism	Yes	No	No	No

As nouns, organism is a hypernym of nekton; that is, organism is a word with a broader meaning than nekton:

nekton: the aggregate of actively swimming animals in a body of water ranging from microscopic organisms to whales
organism: a living thing that has (or can develop) the ability to act or function independently

Other hypernyms of nekton include being.

nekton (noun)	organism (noun)
the aggregate of actively swimming animals in a body of water ranging from microscopic organisms to whales	a living thing that has (or can develop) the ability to act or function independently
	a system considered analogous in structure or function to a living body