It's a wave break. The picture is at Lake of the Ozarks, and the docks are for a restaurant. I wish I had screenshots of it, but maybe 2 weeks before I took this recording, I had found that a big school of bass was suspended below a big ball of baitfish that were feeding on the algae on the bottom of the wave break. I got amazing detail, including the cables connecting the wave break to the bottom.
I'm still hitting myself in the head for not taking a screenshot..