water wings vs flotation device

water wings and flotation device both are nouns.

Word	Noun	Adjective	Verb	Adverb
water wings	Yes	No	No	No
flotation device	Yes	No	No	No

As nouns, flotation device is a hypernym of water wings; that is, flotation device 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
flotation device: rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning

Other hypernyms of water wings include life preserver, preserver.

water wings (noun)	flotation device (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