I need a specific shader

Hello fellows developers!

I need a shader for a underwater surface. My game is totally underwater and there is nothing but sky above the water. The player never sees the surface from above.

So what I am after is a shader that will only be visible from below. It needs to work with unity fog in forward render, gamma color space, and it gives a looks similar to this: https://outdooruae.com/wp-content/uploads/2017/12/OB-4.jpg
and this: https://s3-media4.fl.yelpcdn.com/bphoto/5cJaKFkxii33SUID9SGsrA/348s.jpg

It can be faked, I don't care how the look is achieve as long as it looks similar to those picture "snell's window". It has to run smoothly in iPhone 6 and above and Android 6 and above.

Again, all I care is that it looks like that, don't care to be accurate, or actually refracting, all I care is that it sells realism.

Let me know if you can do this, how much would you charge, and how long it would take.

Regards,
Carlos