My sink of thirty-five years: 3/4 inch marine plywood, fiberglass cloth covering the bottom and a couple of inches up the sides and all including the tops* coated with marine polyester with almost 18% gray coloring added.

* loose 3/4 inch plywood pieces that can cover the the sink to make additional work surface when the sink is not in use.

http://www.jeffreyglasser.com/