mariner vs sea dog

mariner and sea dog both are nouns.

Word	Noun	Adjective	Verb	Adverb
mariner	Yes	No	No	No
sea dog	Yes	No	No	No

As nouns, mariner and sea dog are synonyms defined as:

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

mariner (noun)	sea dog (noun)
a man who serves as a sailor	a man who serves as a sailor