We've been testing underwater caustic effects for our next game. Here is a look at our latest test in Unity. It's interactive and in real time: We've posted the video here http://www.youtube.com/watch?v=GOSLL0FOYP4&feature=youtube_gdata_player Jacob has also created a short write up and included some code samples here: http://www.jupitermoon.com/2012/09/21/effective-real-time-caustics/