I have been using a Sony RX-100 with a Nauticam housing and a Sea & Sea 110a strobe, in TTL mode. Underwater, the exposure compensation of the camera's flash does not work. I bracket it from 0 to -1 and to -2 and nothing changes in the exposure of the subject lit by the flash. I do the same test "overwater", with the camera in the housing, and the flash's exposure compensator works!
I use aperture (apples's software) to import my pictures and I noticed on the EXIF info, under flash exposition, I get "Return Light not detected" on underwater pictures, while on the "overwater" pictures I got "Return Light Detected". Is this the problem? any ideas?
Despite of this issue, the TTL system provides a very smooth and nice light.