Drain your boat ...
when you pull it out of the water. Leave the plug out when you have it stored for the winter so that water that may enter and otherwise freeze if you left the plug in, will instead drain out.When I was a kid, my 14' sailboat had a drain in the bottom that would let water out as long as you were moving. This way, after a capsize, you could get the boat sailing along and then drain the remaining water out. You need a boat with positive flotation for this to work. I suppose you could try it if you have a boat that is capable of being righted and sailed after a capsize, but I have no experience with an O'Day 15.