intentional hole in waterproof box

[rokenbuzz]

I'm going to try to use a watertight box to house my electronics.
I'm expecting dives of no more than 10 feet and this box is only rated IP86, so I know I am pushing it.

Plano Guide Series 1470-00 Size Polycarbonate Field Box:

plano.PNG (78.21 KiB) Viewed 4829 times

As a test, I filled it with rocks and left it at the bottom of an 8 feet deep pool overnight and it had no leaks.
Later I was looking closer and I saw it is manufactured with a tiny 2mm hole in the front. The front handle snaps down and has a circular rubber pad that covers the hole.

planohole.PNG (196.11 KiB) Viewed 4829 times

I notice I can put pressure on the lid as I close it, pushing air out. When I unclamp the front, unsealing the hole, I hear the hiss of air entering.

What is this hole for? Should I leave it as is?

[Bennachie]

The hole is probably there for safety reasons, in case pressure builds up in the box from rotting food, or altitude change or whatever.

If you don't block up the hole the box will leak. Simples.

A tip- mount the box upside down on the ROV and fit any penetrators in the lid (now the base!). Also mount any boards on small pillars attached to the 'lid'. Don't drill any holes whatsoever in the main body of the box. That way, even if the seal leaks, the main part of the box will act as a 'diving bell' and will stay largely dry.

[rokenbuzz]

Oh wow, that's a great idea about flipping my box upside-down!
Thanks!