On the Paralux flashlight I inspected at a store before, I think the package stated that the light is only water resistant
, not waterproof, so I don't know if the warranty covers use of the light while diving.
OT: This incident made me recall the time I had to dive into our fishpond to assist my daughter who had fallen off her raft. I still had all my gear on, including my Surefire E2e. I was in the water for a good 20 minutes before I got out and took everything out to dry. All I can say is that the O-ring seals on the Surefire are pretty good, since the light is still working up to this day
Edited to add:
Each CR123A lithium battery (Panasonic or Sanyo brand) costs around P130 to P150 in photo supply stores. I heard that they are cheaper in Raon, though I don't know by how much.