Realistic Water Shader for Godot 4

This is a work in progress port of Godot Realistic Water to Godot 4.0. A writeup of the porting process is available here, and a brief clip of the shader running under all three renderers in Godot 4 is available here.

The original shader was created by UnionBytes, Achim Menzel (alias AiYori). That project, and this port, are available under the MIT license.