In the Learn tab of the Epic Games Launcher, there is free Content. There is a free project called Water Planes which has three different types of professionally made water shaders, one of which being a lake like material. Create a blank 4.8.3 project, add the Water Planes content to your project. Then upgrade that project to 4.9.
You can also take a look at a tutorial on the Wiki
Translucent Water Shader Tutorial
I hope this helps!