The cheapest way to use calcium chloride in the offseason is to purchase it in bulk as a sidewalk ice-melting product. When purchasing, be sure to read the label to ensure it is calcium chloride and not a different melt product. Pour several pounds into a large container, like a drywall compound bucket — or better yet, two or more — and leave the buckets out in different parts of the boat before covering for the winter. In the spring, you'll find the dry crystals fused into a mass of puffed-up little white balls, possibly with liquid at the bottom.