How to create a simple pool?

hi just a simple question, i’m trying just to creat a pool that swim in , i would like to know how to make a water volume with realistic underwater !

-ive allready made a custum shader for the water using plane

-and put a Physics Volume but that the tricky part, in fact i totaly don’t understand how it works ahaha!

-for the underwater i gess i should use a postprocess volume and some custom particles and fog i think i can handle it but

I realy NEED help for physics of the water

im using the (FPS_template by the way)

thks to all !

found finaly for physics !! but just wanted to know if we could make physics simulation caustic or do i have to create a shader thanks !