Change modes UW with a twisty?

[Buster1dog]

What's the opinion on this.
Is it advisable to change modes while submerged with a twisty tail cap?

 

[jspeybro]

I have modded a ultrafire W200 to a multimode with P7 and 18650's. It doesn't have a twisty tailcap, but the head twists and is used to make the electrical connections, so I suppose that is the same as a tailcap.
It works fine. I've switched modes with it underwater without problems, altough I think I only did this above 10m depth until now. Also, the W200 head has 3 o-rings to seal it where you are twisting it, so this may be different from a tailcap.

 

[AnAppleSnail]

I suspect it's sort of a gamble. If there are rough spots in the O-ring, you may give water a chance to get in. However, the minor expansion of the flashlight shouldn't make much difference, since it begins at 1 bar inside and never pressurizes much.

 

[Buster1dog]

These lights are marketed as dive lights but the design is flawed.
Not only the added stress by twisting the tail on it's O-rings but the tail/body connection only works as designed in water as long as the anodizing stays intact.

I've got a TR DF-003. It's got 2 step threading and 4 O-rings in the twisty tail cap.
1st dive with it and it was shorting through the water where the anodizing had failed.
Couldn't change modes out of strobe and couldn't turn it off.
I didn't want to unscrew it more than about 1 turn.
Now I just turn it on to high before it gets wet and leave it alone till I'm back topsides.
Would be nice to have the option to turn it off underwater to look at the biolumescence on night dives. Guess I can just stuff it in a bc pocket for short periods.