Yes! I made stuff like this for my 2115 project! It was a mesh/material-based system, not post-process, though. I placed a single mesh with a bunch of ray beams shooting down in the water. Then I used my own custom code to map a texture to it, pan, and shift the UVs so all the godrays don’t appear to be the same object. But be warned, this method involves the use of a ton of translucency, which is quite expensive unless you have the hardware for it.
You can use the fresnel, pixel depth, and depth fade material nodes to make a material like this: fresnel makes the cones brighter in the center than at the edges, pixel depth can make it fade out as it is positioned further away, and depth fade can blend the light into any clipping planes with a smooth falloff. Once you have the material, map it to any model of a cone (preferably one with smoothing groups), and it will behave accordingly. Place those models as you would anything else, just make sure the material’s additive and the models are set to not cast or receive shadows. I would also use static lights to model the cone in lightmass so you have correct light bouncing. It’s not a perfect solution, and it’s expensive, but if you can get it working properly (especially once combined with particle effects), it’s beautiful.