In preparation .... Simple example of caustics in Mental Ray, also using the submerge and glass lume shaders. NOTE: These scenes were created in 3ds Max 8. A lot has changed in how Mental Ray works since then. A newer tutorial is in production to show how to use these shaders in 3ds Max 2009 Design - see here.
Simple caustics in Mental Ray
This Video shows a pool using submerge and caustics - click to play