boater vs paddler

boater and paddler both are nouns.

Word	Noun	Adjective	Verb	Adverb
boater	Yes	No	No	No
paddler	Yes	No	No	No

As nouns, paddler is a hyponym of boater; that is, paddler is a word with a more specific, narrower meaning than boater:

Other hyponyms of boater include canoeist, ferryman, gondolier, gondoliere, rower, punter.

boater (noun)	paddler (noun)
a stiff hat made of straw with a flat crown	someone paddling a canoe
someone who drives or rides in a boat