The rubber ring that keeps the water out of underwater camera housings. This is actually part of an extremely clever sealing system that becomes more efficient as the pressure difference between inside and outside increases. The cleverness lies not so much in the ring itself, but in the shape of the groove in which it sits, which is designed so that the pressure forces the rubber into the gap through which the water is trying to pass.
Consequently, and perhaps surprisingly, an underwater housing is more likely to leak at shallow depths than at great depths. One thing that will disrupt the operation of an O-ring seal however, is dirt, which creates gaps and channels through which the water may creep. Good husbandry in underwater photography therefore, lies in the matter of cleaning the O-ring and the O-ring groove meticulously before closing the housing.
Types of Seal
