I seem to recall several years ago when I purchased my Surefire M2, the folks at Surefire told me they were rated waterproof to 33 feet and if you ordered directly from Surefire and communicated your need, they could get you one verified to 66ft. You may want to call them and talk to them to verify.
Peace
But the M2 will not accommodate 18650 cells... one of the OP's criteria.
AFAIK the M2 does include the extra O-ring in the switch-cap... one of the reasons (albeit a minor one) I chose the M2 over the C2. The extra gasket improves water resistance over other models.
Can the M2 be bored out, to a larger diameter to use 18650's?
Righty
Are any of the P60 hosts rated as water proof? I would love to buy one that will take 18650's.
I love my Malkoff P60F, and want a good home for her.
Righty