A hydrostatic pistol actuated by water pressure at a pre-selected depth detonated the charge. Initial depth settings were . Because production could not keep up with demand, anti-submarine vessels initially carried only two depth charges, to be released from a chute at the stern of the ship. The first success was the sinking of U-68 off Kerry, Ireland, on 22 March 1916, by the Q-ship Farnborough. Germany became aware of the depth charge following unsuccessful attacks on U-67 on 15 April 1916, and U-69 on 20 April 1916. The only other submarines sunk by depth charge during 1916 were UC-19 and UB-29.
