Hi, here is a video I put together from my scuba diving in Grand Cayman. All shot with a G15 and Canon WP-DC48 housing and ambient light. I had a 750 lumen i-torch but couldn't get the right settings.
Custom WB was used every 3 minutes or so or as the depth changed. Even at 100 ft I was able to get some color back. My GoPro lost all color at 25 ft without a filter.
I'm very happy with the camera and housing considering the housing is significantly cheaper than other brands: