If your boat is a 14-foot aluminum john boat, then the old standard plastic seat attached with a swivel bolt will probably do. If you want to build a high-quality seat in a fine boat, then you may be interested which high-end woods that are best adapted to marine use. The four finest quality marine lumbers are made from teak, jatoba, mahogany and cedar.
Teak, or tectona, is a long-lived tropical birch. Teak is thick-fibered, making it cut easily and evenly. Teak is resistant to warping and has few knots. It is rich brown in the heartwood with a well-defined white ring in the outer wood. Teak is one of the strongest woods in the world, and produces a natural oil that makes it resistant to water, insects and bacteria. Teak is very expensive, and its production is stressful to fragile tropical ecosystems.
Jatoba is also called Brazilian cherry, though it is not a true cherry. It is grown in Brazil, but also in Peru and Mexico. Like teak, jatoba produces its own water and insect resistant oil, which is why it is sought-after as a high-end marine lumber. Jatoba has a burgundy heartwood and is somewhat cheaper than teak. It is resistant to warping -- a very desirable characteristic for marine woods -- but its density makes it hard on tools. Carbide-tipped cutting tools are recommended for jatoba. Jatoba sands easily, however, and the natural finish is striking.
Most mahogany is also grown in Latin America, where aggressive harvesting has diminished the tree’s range and made the lumber more costly, as well as an ethical dilemma for some woodworkers. Mahogany’s extreme density gives it good water and insect repelling characteristics; and mahogany tools easily, making it a favorite for wood carvers. Mahogany heartwood ranges from blond to deep reddish brown, and finishes to a lustrous natural surface.
For those who want to avoid tropical woods for financial or ethical reasons, but who still want a warp-resistant wood that repels water and insects, cedar may be the best choice. Cedar is considered the best choice of North American wood for outdoor furniture like boat seats. Not only does cedar have a salmon finish and good moisture characteristics, it produces a chemical called thujaplicin, which gives cedar its peasant aroma which also repels insects.