WARNING: Do not upen your underwater camera case outside.
REASON: The warm moist air will get inside and then when you put the camera into the cooler water, the moisture will condense out and cover the inside of the case with tiny droplets. This will effectively cover the lense of the camera and you will end up with no usable pictures. Luckily I found this out after our snorkeling trip when we were playing around with the camera in the swimming area, so my snorkel pictures are fine.
RECOMMENDATION: Only open the camera case inside where the air conditioned air is cool and dry.