Polyethylene is the material commonly used for boat seats. A 1 lb to 1.5 lb density polyethylene provides a comfortable cushion as well as personal floatation in case of an emergency. Polyethylene will float approximately 55 lbs per cubic foot so a seat cushion that is 2” x 12” x 72” will float approximately 55 lbs. Polyethylene is available in a variety of sizes and can be custom fabricated for many different applications.