Mold and mildew are risks of tightly wrapping a boat for the winter. There are crystal pellets that absorb moisture that will help. The right tarp also helps. Shrinkwrap that is not properly ventilated may lead to rust and mildew. With the best boat tarp, you’ll have years of protection for a much lower price. Plus, the tarp is reusable and won’t add unnecessary plastic to the landfill in the spring. here