A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

water boat • water craft
water boat—(hist.) a boat carrying fresh water to ships: He
built some water boats and, by these boats furnished the gar-
rison with good water.
water craft—a boat or boats: The object lying upon the table
was a ten-foot model of a strange-looking water craft.
water boatman • water-man
water boatman —a water-bug (Notonecta glauca), whose
body resembles a boat: The water boatman, an insect related
to the Cimicidae, made me suffer still more severely.
water-man —
1
. a man who rows or lends out small boats for
pay: A coachman, postboy, or waterman, generally expects
some grace from the passengers, over and above his fare. 2. a
man employed in the distribution of water: Duran is the water
man. Maneuvering his 
1
5-ton tanker down narrow ravines,
he delivers water to people the city cannot afford to supply.
3. (hist.) an attendant at coach-stands, whose primary function
was to water the horses: The waterman darts from the pump,
seizes the horses by their respective bridles, and drags them,
and the coach too, round to the house. 4. (coll.) a water-color
artist: The collection of water colors includes among its con-
tributors many of the best living “water-men.”
Note: 
a) The compound does not correlate in meaning with
the noun seaman— a mariner; a sailor : Seamen in the mer-
chant vessels are required to enter into a contract in writing
commonly called shipping articles.
b) The compound is not antonymous in meaning to the noun
landman—(also: landsman) 
1
. a person who lives and works on
land (as opposed to seaman): Up to a third of the crew in
wartime were landmen, who had volunteered to serve. 2.
(Petroleum Industry) land consultant responsible for obtaining
permission to drill an oil well, build a pipeline, etc.: I was a
landman in Texas and Illinois (in the good old days) before
the bottom fell out of the oil business.