Above we see some examples of water cannon in use by S. Korean, Indian, Taiwanese, and Japanese coast guard vessels and a Navy patrol craft supporting a Coast Guard mission, attempting to extinguish a fire. Looks like water cannon might be a handy thing to have.
On this original concept model of the Offshore Patrol Cutter there are four water cannon, two on the roof of the hangar and two on top of the superstructure between the Mast and the stack.
On later illustrations, the water cannon seem to have disappeared.
Am I missing something?