Hello,
I did a pressure test before going into the water, and after 15 minutes of vacuuming, the negative pressure didn’t change. So we put the robot into the water, but after the robot was in the water, the electronic compartment was filled with water (I can be sure that the OK knob was tightened). What is the reason for this?
Hi @Kingzeon,
I’m not sure what’s most likely to have gone wrong here. It’s definitely unlikely for the enclosure to fail so soon after passing a vacuum test, unless something was removed or not properly inserted before it was put into the water.
Is it possible the o-rings were damaged (or not installed) on the vent plug?
I would recommend contacting support@bluerobotics.com and linking them to this thread - they may have some other ideas as to what could have gone wrong, and they’ll be able to sort out a potential replacement or refund if the issue was on our end 
Hello Eliot,
After the vacuum test, nothing else was removed or inserted.
The o-ring on the vent plug is installed and not damaged.
Is there anything else that could cause this phenomenon?
There should be two o-rings there - is there one missing?
Not that I can think of, unless perhaps your vacuum tester is blocked somehow (in which case maybe you weren’t actually vacuum testing the enclosure). I’d recommend contacting support, as I mentioned in my last comment.