Its water proof by design! put some silicone grease on the tube screw it down, silicone grease the case back screw it down with the proper tool you can get on ebay and go for a swim. Or you can send it to VAC and he will pressure test it for you to 3 atmospheres that's about sixty feet. 1 atmosphere is on land at sea level.
Thanks Thrasher - I built a pressure tester here at home with a water filter housing (link around here somewhere)... I think it goes to 4ATM. I just haven't had time or motivation to clear off my workbench and do some testing. I'm sure it is waterproof. TC does a great job and I'm sure it'll pass.