Recently, I spent a couple days in central Florida. We only had time for a few dives - one in Crystal River, one in Alexandria Springs, and one in Blue Grotto (plus a manatee snorkel). The first time I've done any of those locations. It was also the first time I've been able to take my new em1mkII underwater and I was pretty psyched. Since the average depth of most of the dives was <10ft., I thought I would keep things simple and just shoot with ambient light. This is not something I've done very much - I almost always shoot with strobes.
I was surprised by the amount of backscatter in most of my photos, especially given the generally clear conditions. It sure looks like backscatter to me at least. I hadn't really been worrying about it, since I always associated backscatter with strobes. Can others comment on backscatter occurring in ambient light and tips to minimize it? There was certainly particulate in the water, but it appeared generally clear with good viz.
Here's an unretouched example: