Abstract: This device is a spear gun for underwater fishing and is operated by a reservoir of compressed air. A reservoir is maintained in an elongate gun barrel within which a slidable piston is located between the pneumatic valve end the other or spear discharge end. A shock absorbing cushion is provided at the discharge end of the gun barrel for stopping the travel of the piston without damage. A gun stock is secured over the gun barrel adjacent the discharge end, and remote from the valve end. The spear rod is provided with a conically reduced portion leading to an abrupt radial shoulder against which shoulder a V-shaped lock is pivoted in the bottom of the spear gun to abutting position to hold the spear in position ready for firing. An L-shaped sear is pivoted to a trigger rod slidably reciprocable through bearings for releasably engaging the V-shaped lock.