WordNet (r) 3.0 (2006):

watercraft
    n 1: skill in the management of boats
    2: a craft designed for water transportation [syn: vessel,
       watercraft]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "watercraft":
   aircraft, argosy, bark, boat, bottom, bucket, carriage, carrier,
   conveyance, craft, hooker, hulk, hull, keel, leviathan,
   medium of transportation, packet, ship, tub, vehicle, vessel