boatman vs paddler

boatman and paddler both are nouns.

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

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

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

boatman (noun)	paddler (noun)
someone who drives or rides in a boat	someone paddling a canoe