- Edited
I had the same problem with water shader tutorial before.
https://godotforums.org/d/30053-confuse-on-the-doc-s-your-second-3d-shader-water-tutorial/6
As for the school of fish I don't know but for the basic idea for the Shader script:
-float is like var
-uniform is like export var
-codes in void vertex() are for controlling the shape (3d model's vertices)
-codes in void fragment() are for controlling appearance (color, texture..etc)
so VERTEX.x += cos(time) * side_to_side;
should be placed in vertex()..etc
But yea they should've included the final codes or example project for us to study.