That's interesting
I am going to assume you know that the purpose of boat bottom paint is to inhibit marine growth, not just to look pretty, and that house paint won't fill that bill. If you are taking the boat out of the water after each use, you don't really need bottom paint. That being said, I would worry about putting plain old latex paint on your boat. House paint is not formulated to be underwater, but it does seem to be remarkably resilient, so I bet it would look good for awhile if you boat in fresh water. Of course when it does come off, it will come off ugly, peeling and blistering. Remember too that latex paint is formulated to be applied over primer or other latex paint, so if you want it to last and look pretty, do your prep work.