The Collaborative International Dictionary of English v.0.48:

Boatman \Boat"man\, n.; pl. Boatmen.
   1. A man who manages a boat; a rower of a boat.
      [1913 Webster]

            As late the boatman hies him home.    --Percival.
      [1913 Webster]

   2. (Zool.) A boat bug. See Boat bug.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Boat bug \Boat" bug`\ (Zool.)
   An aquatic hemipterous insect of the genus Notonecta; -- so
   called from swimming on its back, which gives it the
   appearance of a little boat. Called also boat fly, boat
   insect, boatman, and water boatman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

boatman
    n 1: someone who drives or rides in a boat [syn: boatman,
         boater, waterman]