able-bodied seaman vs sea dog

able-bodied seaman and sea dog both are nouns.

Word	Noun	Adjective	Verb	Adverb
able-bodied seaman	Yes	No	No	No
sea dog	Yes	No	No	No

As nouns, sea dog is a hypernym of able-bodied seaman; that is, sea dog is a word with a broader meaning than able-bodied seaman:

able-bodied seaman: a seaman in the merchant marine; trained in special skills
sea dog: a man who serves as a sailor

Other hypernyms of able-bodied seaman include gob, Jack-tar, Jack, mariner, old salt, seafarer, seaman, tar.

able-bodied seaman (noun)	sea dog (noun)
a seaman in the merchant marine; trained in special skills	a man who serves as a sailor