I have Xtar D20B 1000 light. On surface it works properly. It turns off, on and changes modes. But at depth of only 10 meters I can't turn it off completely. No matter how much I turn it's head (I almost unscrew it) it's still on but on very low level of brightness. And if it on SOS mode it's still blinking at very low level of brightness. Is it bug or feature? Can I switch it off underwater completely? Can I fix this behavior by myself? I use it as a backup light and really want it to be off most of the time.