Well I wasn't able to go the day they went, but someone else who was interested in this light took it to the local quarry to dive with it recently.
The quarry is only about 45 feet deep, but no leaks or problems after using it for a couple dives of close to an hour. While this isn't an "extreme depth" test, it'd definately deeper than just "immersion".
If you want to read his full review, see post #10 of this thread
Dorcy brand dive light. Anyone used them? - ScubaBoard
BTW... I've replaced the lanyard that came with it. but on a home made one, which I didn't like and soon replaced with a much better one. still need to post some pics of it...