Could it be that the "item" you're having problems with is intended to be used as a "negitive boolean" object, and should be grouped with a "positive" water or sea... ya know... to kinda hold the water out of your boat ?? I've modeled lots of boats. If it's an "open" boat, I always have to model an object to boolean cut the water from the inside of the boat...so it doesn't look like it's sinking all the time. Just a guess.. Mikey :O)