Navy SEAL vs sailor boy

Navy SEAL and sailor boy both are nouns.

Word	Noun	Adjective	Verb	Adverb
Navy SEAL	Yes	No	No	No
sailor boy	Yes	No	No	No

As nouns, sailor boy is a hypernym of Navy SEAL; that is, sailor boy is a word with a broader meaning than Navy SEAL:

Navy SEAL: a member of a Naval Special Warfare unit who is trained for unconventional warfare
sailor boy: a serviceman in the navy

Other hypernyms of Navy SEAL include bluejacket, navy man, sailor.

Navy SEAL (noun)	sailor boy (noun)
a member of a Naval Special Warfare unit who is trained for unconventional warfare	a serviceman in the navy