For a pool, my thought would be to fake it by projecting the caustic pattern using a light - as an example in 3ds Max, add a spotlight, set to rectangular, open the Advanced Effects tab, drop a texture that represents the colours of swimming pool caustics (should be plenty of free ones out there on the web) into the Projector Map box, then to make setting it up easy I'd ensure the walls and floor of the pool are separate objects and use an Include / Exclude list under General Parameters so that the light only affected those.
Hope this helps!