The caustics affects is, how can I say this, interesting to use.
Here are some tutorials that will get you started: The Caustics After Effects tutorial by Eran Stern
The hardest part is making a displacement map to make caustics look realistic. The best results I overachieved were created by filming a ripple tank but I built in the studio with 3 mil black plastic tarps and 2X4 framing with about an inch of water and some back light. I also wants to use iPhone footage of a small creek near my house shot on an overcast day. The water was nearly black.
That clip is most definitely shot for real with the texts and graphics superimposed and using the massaged footage as a displacement map. Even if you had spent the last ten years doing nothing but trying to master the Caustics effect, you probably never could achieve that level of detail and the dynamics artificially.
Appreciate the input! This was actually the answer I was hoping for as shooting the water is much simpler than learning Caustics. I'll do some research but could you point me in the direction of how to create a displacement map from the footage? I was thinking film the water with a side light and back background and try and use a screen opacity so only the highlights show?
The combination of real footage and caustics is extremely powerful and actually quite easy to use once you understand the workflow of caustics. An overcast day yields gray water that is very easy to use as displacement maps. The use of a polarizing filter can help. Creating the caustics displacement map with wave world or fractal noise is the hard and long way to go.
The best Caustics are created by first using Wave World to build the reactive input. Brian Maffitt his very own self created the finest tutorials for both.