Maybe I have been extremely lucky but I have a hero 1 and a 3 and a 4 that have always been stored with the door shut, and they still goes on tech dives without issue. There is no special care involved with a GoPro other than a quick rinse after every dive. I own 3 GoPro's and do a lot (weekly) of deeper diving, and have yet to flood a camera. On the contrary I store my camera in its housing with the door shut to protect the camera and it's lens. I often wonder if some of the care "tips" that I have seen are related to some of the flood issues that I read about. I wonder this because over the years I have used, abused, and tortured my cameras, and they seem to just keep working. The only advice I can give is to inspect your housing seal before the dive and be sure it does not have any hair or debris or damage on it before sealing. I also try not to unseal the camera once in the humid outdoor air when I am going to dive unless I have to. It is my opinion that greasing the seal, or in any way futzing with it, is a bad idea. Leaving the seal open and exposed seems to be path to dirtying/damaging the surface of the seal. I also toss out the new stock housing and use the hero 3 "dive housing" I feel the newer housing is flimsy and unsuitable for my needs. The dive housing is much more robust, and for the price of the Hero4 Black, it's cheap insurance.
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