A common solution for marine applications is a two-part urethane foam, also called pourable urethane and liquid foam. The two-part liquid, expanding urethane foam, is a closed-cell, pourable foam, which will resist the absorption of water. Once fully cured this foam can be laminated over with any type of polyester, epoxy, or vinyl ester resin without melting. This product can be poured in multiple coats.

Ten Gallons yield 40 cubic feet of 2 lb density foam.