Watch pressure testing: dry vs wet?

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Originally Posted by W&D

Apologies for reviving an old thread but I think I may have been testing my watches in a wet pressure testing device incorrectly?. I pressurised the watch dry in the chamber and then dunked the watch into the water to look for bubbles but didn't release the pressure until AFTER I pulled the watch back out into the dry area. I assumed as water cant be pressurised that the bubbles would show if there was a leak?. Am I wrong on this?

The water will not compress, true, but the pressure in the case will still be the basis against which the watch internal pressure reacts. If you do not release the case pressure, then there will not be a lower pressure point (the above air void) that your potentially positive pressurized watch will "leak" to.