Lightweight, Non-Absorbent Marine Composite Panel

Coosa Board Bluewater 20 is a fiberglass-reinforced composite panel engineered for marine and high-humidity environments where plywood commonly fails. Manufactured from high-density closed-cell polyurethane foam reinforced with continuous strand fiberglass and woven roving, Bluewater 20 delivers impressive strength without the weight and moisture concerns of traditional marine-grade plywood.

At 20 lbs per cubic foot, Bluewater 20 is more than 45% lighter than plywood, making it one of the most practical lightweight plywood alternatives available for boat building, RV construction, and marine fabrication projects.

For applications requiring additional rigidity, compare it to Bluewater 26 to choose the right density for your build.

Coosa Bluewater 20 vs. Coosa Bluewater 26

Bluewater 20 is the lighter and more economical of the two Coosa composite panel options. It’s ideal as a semi-structural or non-structural core material where weight savings and moisture resistance are the priority.

If your project demands higher compressive strength and stiffness, Bluewater 26 composite panels provide higher density and added rigidity.

For budget-conscious transom repairs, floor panel replacements, and hatch lids, Bluewater 20 is typically the right balance of performance and cost.

Common Applications for Coosa Board 20

• Boat deck flooring and floor panels
• Transom boards and transom replacement
• Hatch lids
• Wall panels and slide-outs
• Marine composite decking

Bluewater 20 is available in 1/2" and 3/4" thicknesses and sold in 2' x 4' panels, with quantity discounts starting at 5 sheets.

For bonding, laminating, or sealing your installation, browse marine resins and coatings that pair well with composite panels.

Coosa Board 20 FAQ

What is Coosa Board?

Coosa Board is a brand of fiberglass composite panels used as a lightweight, non-absorbent alternative to marine plywood. The panels are made from closed-cell polyurethane foam reinforced with fiberglass, making them resistant to water, mildew, and rot.

What is Coosa Board made of?

Coosa Board is constructed from high-density closed-cell polyurethane foam reinforced with continuous strand fiberglass and woven roving. This construction provides strength comparable to plywood at a fraction of the weight.

How does Bluewater 20 compare to plywood?

Bluewater 20 is over 45% lighter than marine plywood and will not absorb water, swell, delaminate, or develop mildew—common failure points for plywood in marine environments.

What thickness of Coosa Board should I use?

Bluewater 20 is available in 1/2" and 3/4". For many non-structural applications like hatch lids, wall panels, and floor skins, 1/2" works well. For transom replacement or applications needing more rigidity, 3/4" is more common.

Can Coosa Board be used as a transom replacement?

Yes. Coosa Board—especially Bluewater 20 and Bluewater 26—is widely used for transom replacement because it won’t rot or absorb water like wood.

Is Coosa Board available at Home Depot or Lowe’s?

Coosa Board is a specialty composite panel and is not typically stocked at Home Depot or Lowe’s. Fibreglast carries it in stock with volume pricing and ships direct.