A friend of mine bought a house on a lake in september. We took the dock out of the water for the winter. It has three aliminum sections with 3 plastic floats each under them.. There suposed to be air tight but the dock was sitting in the water low before it came out because there was water in the floats. I was wondering if they could be fill up with some sort of spary foam so the would float like they should... Do they make a product like this ????And if so where do you get it.. This house is in NH .. Any info would be great...

find a place that sells fiberglass,resin,marine paints etc. they will have 2 part foam. Be careful with it, its wicked if you use too much