I can vouch for the water resistance of D-Mags. A few years ago, I was at boyscout camp, and myself and several of my troop-mates were heading into the woods for our "wilderness survival" overnight trip. As we were crossing the bridge to get to the other side of the bridge (mind you, we're in the middle of the mountains, at night, being guided by my mini mag with a nite-ize drop in; it was dark:devil
we hear a speluuuunnnkkk, shortly followed by an "oh no!" What turned out to have happened was these two guys were fishing, and one was holding a 4-D mag over the water to shine the fish. Well, he had dropped it. Underneath the bridge, the water is about 15 feet deep. Well, his mag light was shining up at us from the bottom, still running. Apparently, the air trapped in the head was enough to make the head point up.
Long-windedness over now... But, yeah, they're pretty waterproof.
Oh, yeah... They managed to get it out by about midnight, from what I heard, it was still running, so it was easier to find, but the kid who went to get it, was caught by a counselor, and had to go home (we're not allowed to swim in that part of the lake).