Your biggest limiting factors are the dive and explosive ratings. Realistically, no way you'll get both of those in a good $25 light. I was going to say Preon too, but it's not rated. In fact, I think most lights don't need to pass more than a "dunk" test officially.

If you're looking dive, think Pelican brand. If you want explosive, try Streamlight. Other brands have few and far between for those environements.