You need to use a Custom Depth, like it’s in the video, but with inverted values, for apply fog to everything, but water UE4: Stealth Invisibility Effect (With Distortion) - YouTube
You need to use a Custom Depth, like it’s in the video, but with inverted values, for apply fog to everything, but water UE4: Stealth Invisibility Effect (With Distortion) - YouTube