Another great wizardry by BB! :D This is fun to play with! :D To solve the repetitious tiling of the gobo, I used Genetica to make a set of assymetrical seamless caustic tiles and then set up a scrambler material; the colors represent areas where each of the four caustic tiles appear; the black grid shows how big a caustic tile is.

Superfly render settings, with volume samples and volume bounces:

Superfly render:

Zip with the seawater box, seafloor terrain, gobo, and the texturing image maps [undersea godray kit]

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5