Are these flexible housings really waterproof ?
Yes, flexible housings are 100% waterproof !
All our housings are absolutely water-tight. We have been manufacturing this kind of housing since 1970. Had our housings not been renowned fo their waterproofness, we would not have been known this long as the leading manufacturer of water protection for cameras and would not have sold over 850.000 units world wide.
The foil is formed and welded on special machines, some of which have been tailor made for our products. Every single housing is subjected to a series of rigorous tests before being made ready for shipping. All products are manufactured in our factory in Wolfratshausen near Munich, Germany. Quality "made in Germany".
Each time before taking the housing into the water you should make your own test. Who knows if the unit has not been damaged by negligence, vibrations during transport, etc. since you last used it ? Just close the empty housing with as much air as possible, submerge it completely under water and apply additional pressure. If it has a puncture, you will see bubbles rising from the hole, if not, all is well and ready for the next action. As the internal and external pressure are always the same in the flexible housings. (the air inside the housing gets compressed as you dive), a housing that is waterproof at 1 ft. will also remain waterproof up to 100 ft and more.
There is a groove at the rear of the closing rail. As you submerge the housing bubbles will escape from this grove. This should last for about 1/2 Minute and before coming to an end. This phenomena is normal and has nothing to do with whether the housing is waterproof or not.
Please also check the following section: "Flexible housings: What's that ? And how does it really work?"