I was out in the Nullarbor caves over Easter, shooting for a client. Once we were done with work my buddy and I headed off to a different cave to get a few dives in. The video from one dive is below. It was half shot with my Canon 5DII, half with my buddy's GoPro. He's the diver in black, I'm the diver in yellow. If I'm in the shot without the camera, my buddy is getting to grips with his first go at a dSLR. He had a good crack at keeping it steady!
Olwolgin Cave is characterised by stunning rock formations and haloclines in the water, so I needed to shoot through water that hadn't been swum through yet. Most of the shots are pushing the camera forward slightly to prevent the fuzzy water from enveloping the dome port.
Here are a couple of shots taken of the same cave system, both on the breathers and on the subsequent dive in sidemounts. You can see the stirred-up halocline water under my knees in the first shot.