How can i create a water reflection lighting effect?

I need to create an animated lighting effect that would look like sunlight reflection refracted through water, like this
does anyone know a way to do this?

 

I wonder if you could use a light from beneath with a cookie mask?

 

are you sure animated light cookies are a thing?
regardless i don't know how i would produce the animation for that cookie anyway, so is there a way it could be calculated inside unity, maybe with like a water shader or something, like in here?

 

That image is of a webgl demo which is calculating the caustics in real time, which is pretty cool. It's also almost the only thing it is doing.
http://madebyevan.com/webgl-water/
There's no reason you couldn't use something like that technique to create a light cookie or projector in real time, but it relies on having a plausible water simulation running at the same time. There are a ton of tutorials out there for how to do this effect with various techniques (usually using a pre-rendered texture), as well as assets on the store.

 

There are tools that can generate an animated tiling caustics texture for you. With specific shaders you can project them onto surfaces for for example directional or point lights. (You calculate where the light hit the water surface to determine the uv coordinates for the caustics texture.)

It looked pretty convincing in a demo we did years ago:

No caustics simulator there, just an array of textures. (About 32 I think.)

The key is to use a custom shader to get the projection right. A simple projector on a light won't be correct, because the caustics texture should be mapped on the water surface.

 

some of these effects could be faked with time dependent 2d noise functions in the shader. There are a couple different noise functions out there and doing some math on them can yield the desired effect. Could be faster than using real animated textures, but might also not offer enough artistic control.