Originally Posted by
GrumpyDiver
While I don't have an underwater housing for any of my still or video cameras, I've done enough diving with people that had cameras along, so in extremely cold water. They would prep their cameras in a dry environment so that there was little moisture sealed into the underwater camera housing.
I can certainly remember doing dives that lasted over an hour and never saw any condensation issues. Condensation is only an issue when the temperature in the housing drops below the dew point and that is temperature rather than time dependent. That being said, most of my diving has been in freshwater lakes and rivers, which were usually no colder than the mid-40s F. Some of my ocean dives were in the high 30s, but I never did these with an underwater photographer.