Boat with two hulls (9)
I believe the answer is:
catamaran
'boat with two hulls' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for catamaran that I've seen before include "Vessel with paralleltwin hulls" , "Quarrelsome woman" , "Twin-hulled vessel" , "raft of logs" , "Twin- hulled vessel" .)