sea dog vs Jack-tar

sea dog and Jack-tar both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea dog	Yes	No	No	No
Jack-tar	Yes	No	No	No

As nouns, sea dog and Jack-tar are synonyms defined as:

Other synonyms of sea dog include gob, Jack, mariner, old salt, seafarer, seaman, tar.

sea dog (noun)	Jack-tar (noun)
a man who serves as a sailor	a man who serves as a sailor