lifesaver vs life buoy

lifesaver and life buoy both are nouns.

Word	Noun	Adjective	Verb	Adverb
lifesaver	Yes	No	No	No
life buoy	Yes	No	No	No

As nouns, lifesaver and life buoy are synonyms defined as:

lifesaver and life buoy: a life preserver in the form of a ring of buoyant material

Other synonyms of lifesaver include life belt, life ring.

lifesaver (noun)	life buoy (noun)
a life preserver in the form of a ring of buoyant material	a life preserver in the form of a ring of buoyant material
an attendant employed at a beach or pool to protect swimmers from accidents