You don't have to "let water inside the boat" to have moisture damage. It's moisture vapor that's the big issue, not standing water. Of course, being on the water, there's lots of moisture vapor available to penetrate and permeate every wooden or absorbent materials aboard, without a drop of water touching anything.
Lauan can can be had in several quite thin sizes, from 1/8" (3 mm) on up. Well built "stick frame" cabinets, skinned with thin lauan will be cheap, but can suffer from warpage and other moisture related issues, so the usual recommendation is epoxy. An initial sealing coat, plus two over coats if finished bright or a single over coat if to be painted. You can even tint the epoxy, so you can even the color under the over coats or use it as a translucent coating under clear, showing some grain and some color. These panels can also be skinned with vinyl, maybe padded, possibly button tuffed or tuck and roll for that cool 70's look. You can glue (contact cement) all sorts of things to these panels for about any decor you like. Maybe stainless or chrome looking Mylar sheet or copper sheeting, or leather, the only limit is your imagination. There's even "printed veil" products to simulate many surfaces, such as granite, glass, marble, wood, metals, camo, even bubbles or pebbles.
