Abstract: A catamaran boat, especially intended for knock-down disassembly and rapid assembly having a generally rectangular frame. The frame has longitudinal members which are releasably connected to transverse members. At least one of the transverse members is arched upwardly. A pair of pontoons having an upper and a lower section, individually inflatable, are disposed below the longitudinal frame members. The pontoons have a pair of sleeves, fore and aft, extending laterally through the pontoon. Pontoon locks are releasably connected to the transverse frame members and extend outwardly from the catamaran boat. One leg of the pontoon lock is disposed over the pontoon and a bight portion is arcuately connected to a second, substantially parallel, leg protion of the pontoon lock. The second leg portion passes through the sleeve in the pontoon and connects to the transverse frame member forming a loop. The catamaran boat is steered by a pair of rudders.