I was (and am) building an aquarium covered in glass, with all contents immersed with terrain water. I’m not sure if it’s a rendering issue with my poor graphics card (my friend @Polymorphic witnessed this same bug too, not sure what gpu he has) or a problem Roblox has with its rendering.
Generally, there’s the wavy part of the display. However, there’s a cutoff at the bottom and the parts within the water show without the wavy effect. It’s difficult to explain (or visualize) so refer to the image at the top. In this screenshot, there exists a glass pane, but even without it, the rendering bug still occurs.