It was my fault. Isn't it always?
I was doing a PADI OW course (as a student for a mag. feature on Nitrox For Free - I passed with flying colours every section apart from the camera-flooding section!)
I needed to grab some pictures of everyone on the dive deck and only had the housed camera so I whipped the dome port off. You know how with the 12-24mm there is a second extention ring? Well, I must have turned it without noticing. So I whipped the dome port back on (badly as it happened) and jumped int the water with the others. It was obvious what had happened within seconds.
What I found interesting is 1) how difficult it was to get the lithium batteries out of the camera because it needs dismounting from the Subal housing camera chassis with a screwdriver or similar - and 2) how the lithium batteries catch fire so easily! I am told that the lithium is so dangerous at this time it can burn right through your skin and you die a horrible deasth a few years later. I will try to keep you informed on that one.
The only damge to the housing was the leak detector because the battery would not come out easily.
Luckily I kept the air space at the top which saved the synch wiring.
New kit located. Picking it up on Monday.