Water Distortion When Snorkeling

by Ken
(Provo, Utah, USA)

I have a question about water distortion when snorkeling. I was in Guam last week for work, and got a few chances to go out and snorkel. It was beautiful, and oh so relaxing.

One thing I noticed, that I don't recall running into elsewhere, was distortion in the water. In appearance it was like wavy lines in the water, and reminded me of heat haze in the desert. It appeared to be from differing water densities, perhaps fresh water, or different temperatures mixing? While moving forward, the view was very clear and crisp, but if I stopped, the distortion became very apparent. It was easy to capture in pictures, but is not visible in the smaller, lower resolution version I can post here.

I found myself needing to maintain forward motion in order to take decent photos and see fish clearly.

I only snorkeled in Tumon Bay, which is entirely ringed by reef, and very calm.

Has anyone else seen this, and know what causes it? My engineering brain won't let it rest, and I haven't been able to find anything online.