you could just make a weighted "depth charge" only instead of explosives when it hits the ground or reaches a certian depth, a bobber ir some kind of float could be released and whatever ship is near or over it would be registered as "sunk"...only the owner wouldnt have to retreive the peices from the bottom of the lake......it may not be as fun, but im shure whoever put a coulple thousand $ into the ship would be happy (compared to what could have happened if he was hit with an explosion....