Lil Mule's question about floatation in boats made me think about something (which is always dangerous).
A friend of mine, Gil from Wisconsin has a Cobra bassboat. He's getting a little older and less flexible, so it's difficult for him to bend down and clearly seeing the bilge drain hole when he's putting the drain plug in before launching the boat. To further complicate the matter, the livewell intake ports are the same size as the bilge drain and located inches away from the bilge on either side of the drain.
The drain plug will fit into the livewell intakes so unless you've bent down and made 100% certain the plug is in the right hole, it's easy to think you have the drain plug in and launch the boat, allowing the boat to fill with water while you're parking the truck and trailer! 
As you can imagine, that's not a good thing to have happen….
After this happened three or four times, he had to do something. He thought about putting screen over the livewell intakes, which would solve the problem of putting the plug into the wrong hole, but when fish start barfing up chunks in the livewell, when rinsing it out, the screen would plug.
He got a piece of brass rod and cut two pieces that were slightly shorter than the livewell intake through-hull fittings were wide. He then used JB Weld to glue the brass rods across the middle of the livewell intake holes.
Now there's no way he can put the drain plug into the wrong hole and risk sinking his boat, and the fish barf chunks can still pass through the opening without clogging it.
A nice and simple fix! 