The construction is pretty robust. The light is two pieces, a base and a cover, each piece is solid plastic and there is a neoprene gasket between them. The mounting bolts hold the two pieces together. The elements inside are all "potted" in epoxy, with the hookup wires going into the epoxy as well, so there are no exposed conducting pieces. I would expect it to work underwater even with the cover missing.

They are sold for use on tractor-trailers; the big selling point is that they are more durable than conventional tungsten bulbs. According to the web site they are rated for 100,000 hours (22 years of continuous use).