Can someone explain a strange artifact in a photo?

Looks like reflections of the clouds in the water. HEIF files use computational photography, just like jpeg files. If you don’t want as much computational photography, shoot Raw files.

Interesting. I don't think it's a compression artifact. You sometimes see this when a camera moves during the exposure. I'm not sure exactly what the camera has to do to take a picture in 1/1500 s, but it sure isn't simple. It actually looks pretty good-- it's a lovely picture. I ran a blurring tool over two or three spots to disguise some sharp lines of discontinuity, and I thought it worked well.

If you look at the horizontal ripple in the water you see motion artifacts. It’s a result of combing multiple shots to create the enhanced image.

Jeff Donald wrote: … It’s a result of combing multiple shots to create the enhanced image.

Yeah--Jeff Donald's right. it's not motion during the exposure, but rather between exposures. I turned off HDR, because I got those things-- even on a tripod, it messed up some good pictures.

You’re welcome.

The issue is related to several factors. One factor being the askew angle and wide angle (ultra wide?). Objects closer to the lens move at a greater apparent speed. This resulted in the segmentation, as multiple shots were taken. Look closer at the continuous ripple and you’ll see motion artifacts within the ripple.