Abstract: A partially submersible water craft comprising a main hull and a pair of secondary hulls mounted one to each side of the main hull, an arm pivotally mounted at one end to each of the main hull and pivotally mounted at the other end to the secondary hull, drive means between the arm and the main hull and/or secondary hull to cause pivotal movement of both arms relative to the main hull and/or the secondary hull wherein said main hull is movable between a position substantially coplanar with the secondary hulls and a second position wherein said main hull is located below the secondary hulls but spaced in between the secondary hulls.