For a saltwater pool bench, the most durable outdoor bench finish is a marine-grade spar varnish with UV inhibitors if you want a clear wood look. If you are open to an opaque finish, a two-part marine polyurethane topside paint is even tougher. Both outperform the standard exterior polyurethane, teak oil, deck stain, and cheap “spar” blends sold for general outdoor use.
A saltwater pool is a sneaky harsh environment. The water is not as salty as the ocean, but it still contains dissolved salt, and the salt-chlorine generator produces chlorine. Splash-out, overspray, and evaporation leave a fine salt-and-chemical residue on the bench. Add strong sun, humidity, and repeated wet-dry cycles, and the finish has to be flexible, water-resistant, UV-stable, and chemical-resistant. That is exactly what marine finishes are designed to handle.
Marine spar varnish is the best clear finish. Quality products such as Epifanes Clear Gloss, TotalBoat Halcyon, or Interlux Schooner are formulated for saltwater exposure and direct sunlight. They remain flexible enough to expand and contract with the wood, and they contain UV absorbers and light stabilizers to slow bleaching. Build at least four to six thin coats, sanding lightly between coats, and thin the first coat about 10–20 percent for better penetration. Avoid interior polyurethane and inexpensive spar varnish from a home center because they often lack enough UV inhibitors and become brittle.
If you are willing to paint the bench, use a two-part marine polyurethane topcoat. Options like Awlgrip or Interlux Perfection create a very hard, chemical-resistant film that resists salt, chlorine splash, and sun better than nearly any one-part exterior paint. Surface preparation and priming are critical, but the added durability is real.
Epoxy is useful, but it is not the best finish by itself. It seals and strengthens the wood, yet it chalks and breaks down under UV exposure. If you use it, apply epoxy as a base coat and cover it with two or three coats of marine spar varnish or a marine polyurethane topcoat.
No single finish is perfect, but a marine spar varnish is the most durable wood finish that still lets the grain show. Rinse the bench with fresh water regularly to reduce salt buildup, and recoat before the finish wears through—typically every one to three years depending on sun exposure and pool use.