Squirt Gun

My dad was in the Florida keys last winter, and he still raves about the good time that he had on a friend's boat. The boat had some sort of a squirt gun mounted to the rail that sent a 'slug' of water though the air at another boat equipped with the same type of gun. It kept the kiddies occupied all afternoon.

I'd like to buy my father a gun like this for a Christmas gift, but can't seem to locate a manufacturer. Can any of you help?