Underwater Effect in Interactive 2D Fluid Simulations in Unreal GDC 2017

Hi,

I was watching Interactive 2D Fluid Simulations in Unreal GDC 2017 talk by [MENTION=868]Sam Deiter[/MENTION] and i noticed that the when camera is half way under water the post process only happens under water and not above water. Normally when the camera touches the post process it affects the whole camera. Im not sure if the underwater area is even a post process but I would like to know how i can make this too? I was also wondering if the project he used in that presentation will be available soon? I would like to study this project and find out how he created the under water effect. i also noticed this happening in Multi-Pass Rendering Video by @RyanB too.

here is some thread about this