I made a video tutorial showing how to create an underwater caustics effect via light function: UE4 Underwater Caustics Effect | Engine Tutorial | Material in Description - YouTube
You can get the materials shown in the video here: ExportedMaterials.zip
I got the noise texture shown in the video from this marketplace asset: https://www.unrealengine.com/marketp…e-texture-pack
But you can very easily make one yourself or find similar textures on dedicated websites.
Let me know what you think 