Thanks yarik83. One of the key things is a large housing with plenty of inertia. That was shot with a Light & Motion Bluray housing for the Sony FX1/Z1, which is a pretty big housing, plus I had lights attached to it. I wouldn't have been able to make it that smooth with a small housing. My previous standard definition housing had big floats on it to counteract the heaviness of my light batteries, and all that bulk helped the camera stay steady. Plus, there was a nice steady current to drift in and my diving skills were polished as I'd been diving daily for a few weeks by then.
