Overlubing is not good.
Your SureFire should come lubed fine for use.
Taking it underwater... The TailCap is designed with three o-rings (two on the Body and one in the TailCap) so that you can take the light underwater locked out and rotate it on to the momentary position or constant-on, and back to Locked Out without leaks.
Do not Lock it Out too far.
My M2;
Constant on - fully screwed in has the notches at opposite sides of the body.
Unscrewing half a rotation will line up the notches for momentary use.
Unscrewing half a rotation again will LockOut the TailCap so that the Notches are at opposite sides of the body.
So that's one whole rotation anti/counter-clockwise from constant-on (fully screwed in) to Locked Out.
I use the same NyeGel Lubes that SureFire does, and I can rotate the TailCaps with my thumb whilst I'm drawing the M2 from my belt and bringing it to a Weaver (?) grip.
So after you've been underwater (you should rinse the M2 with clean water, and when it's dried, just take it to bits and check the o-rings. Personally, I would stip, clean and re-lube after any dirty/wet activity but then I have bought 2lbs of the Lubes.
If you have any concerns about using your SureFire underwater or in a wet environment, contact Surefire Customer Service, free and they'll be able to help you out.
Al
