The oil based Poly from Minwax is excellent for humid seal. For water splashes, etc (not submersion) use the Helmsman Spar, it is indoor/outdoor poly.
One thing, if you stained with a light colored stain, both oil based poly;s will cause an amber tint to the piece. The Helmsman will be more noticeable. Minwax swears their water based Poly-crylic is crystal clear...but I hate working with water based stains/poly's.