How could I create a water surface and water caustics?

I am trying to make an underwater scene and I have all necessary post processes set up. However, the immersion is a little broken when you look up and you see the sky. How could I create the effect of a water surface when you look up? Also, how would I go about making water caustics on the ground when underwater? Thanks a lot!

To fix the first problem you need to enable Two Sided in the material. Caustics can be created using a Light Function.

Also someone shared a caustics light function material in the forums a while ago if you search in Community Content, Tools & Tutorials section.

Thanks so much! I figured it all out!