swimmer vs jock

swimmer and jock both are nouns.

Word	Noun	Adjective	Verb	Adverb
swimmer	Yes	No	No	No
jock	Yes	No	No	No

As nouns, jock is a hypernym of swimmer; that is, jock is a word with a broader meaning than swimmer:

Other hypernyms of swimmer include athlete.

swimmer (noun)	jock (noun)
a trained athlete who participates in swimming meets	a support for the genitals worn by men engaging in strenuous exercise
a person who travels through the water by swimming	a person trained to compete in sports