Closest we've come to dealing with something like this was after Hurricane Irene, we lost a house we had bought 3 months earlier in Vermont. Got pushed right off its foundation and filled with 3-6" of mud and structure too damaged to salvage anything so it was a total loss. Insurance first gave an estimate of 60-70% of the value since flood insurance is based on depreciated value.. Since we had only bought it 3 months earlier, we argued it hadn't depreciated yet.. fortunately we said the right things and got full payout. Happened in August and we got paid in December I think.

I have not idea what boat insurance is like, but hopefully it would be similar, although my initial feeling is it is probably a bit more drawn out.