Well, I checked my boat that I've had covered on my patio throughout this past Fall & Winter, and I had a giant ice-cube in the bow (gun well) that's about 8 inches deep... Had a leak in the front part of the tarp I cover my boat with - and the bow sticks out about 4 inches from under my patio so I expect that's where the ice build up came from - from the run off above...
Not a big deal however as it's melting and I'm bailing the water out with a cup as the ice melts down. Doesn't appear to be any damage - though my anchor, two life jackets, one black bucket to put fish in (when we caught 'em), and my fishing net, are all froze in the ice a'little bit, but it's melting pretty good right now. We have warm temperatures a coming for the next 10 days - mostly mid to high 40's with a day or two perhaps in the 50's...
I sure as h-ll hope ol' man winter is through with us now...