Abstract: A trigger fired underwater firearm particularly adapted to defense against sharks is described. The firearm has an elongated tubular handle with a cartridge receiving head at one end, a trigger mechanism in the middle, and a safety mechanism at the other end. A longitudinal shaft extends down the tube and has a firing pin at the end which engages the firing head and a safety pin where the shaft passes through the safety mechanism to the external cocking grip. Pulling back on the cocking grip on the end of the shaft stores energy in a firing spring. The firing mechanism uses a cocking notch in the interior elongated shaft to engage a moveable pawl on the end of a firing lever extending through the tube wall. Depressing the external end of the firing lever releases the pawl from the firing notch allowing the shaft carrying the firing pin to advance under spring pressure to hit the firing pin against the cartridge primer in the head end. The cartridge fires through the open end of the head into the target.