water wings vs life preserver

water wings and life preserver both are nouns.

Word	Noun	Adjective	Verb	Adverb
water wings	Yes	No	No	No
life preserver	Yes	No	No	No

As nouns, life preserver is a hypernym of water wings; that is, life preserver is a word with a broader meaning than water wings:

water wings: a life preserver consisting of a connected pair of inflatable bags that fit under a person's arms and provide buoyancy; used by children learning to swim
life preserver: rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning

Other hypernyms of water wings include flotation device, preserver.

water wings (noun)	life preserver (noun)
a life preserver consisting of a connected pair of inflatable bags that fit under a person's arms and provide buoyancy; used by children learning to swim	rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning