When you're inside the waters surface (head level meeting water surface) you experience odd textures.
Here is a gif of the differences:
https://gfycat.com/ShrillHorribleAfricancivet

I use the search button to look for something similar to this, but couldn't find anything.
If this is a duplicate, sorry.

Edit: Upon testing other versions, I either never noticed it, or this has to do something with my own setup.
Please let me know if that is as intended or not, I'm not sure anymore.
Sorry for the time.