According to an aspect of the invention, there is provided a method of triggering an explosive charge of each of a plurality of munitions, the method comprising: launching a first munition, into the air, from a first gun barrel, and into water to engage with a target location, the first munition comprising a first explosive charge and a first fuze system, adapted to trigger the first explosive charge in the water, launching a second munition, into the air, from a second gun barrel, and into water to engage with the target location, the second munition comprising an second explosive charge and a second fuze system, adapted to trigger the second explosive charge in the water, the method comprising co-ordinating the timing of the triggering of the first explosive charge and the second explosive charge to establish a co-ordinated explosive event at the target location.