Hm... no fun for the sub caps indeed
but what caused the subs to sink? I read on the OAF website that their ships are made with thin balsa wood so that the BBs have a chance of going through the hull, a fair chance of sinking for everybody. What are the subs' hulls made of? Regular material like fiberglass, vacuum formed plastic, wood, or else? With underwater pressure, a small hole blasted by a weapon will probably cause a disturbance in the pressure equilibrium inside the hull. Assuming that a sub is dryhull, this would probably cause it to sink. But if it was a wet hull, with electronics stored inside the WTC (Water Tight Cylinder) a BB or something like that would have to have the energy to go through solid plastic.