While we're supposed to be water tight, that's less and less true lately. Last season I was contemplating an overboard bilge drainage system using one of the sea suctions. You could route a little hosing and a couple seacocks so once it was out of the water it would flow out on it's own. Whether you use the engine suction or the head suction, it would double as an alternate way to pump the bilge in emergency. (truly an emergency, because who wants bilge water running through their heat exchanger unless the boats going down?)
But I haven't spec'd out the positioning of the suctions to see if that's feasible. So it's still in the pipe dream phase. (no pun intended)

I hope to check it out for this off season.