Rendering with progressive mode enabled, as soon as the first sample displays, you should see the caustic pattern on the ground; the godrays only resolve gradually. I am rendering only with the CPUs (two Xeon X5690 processors, 24 total threads at 3.46GHz). My old Quadro FX5800 video card is not suitable for rendering this in GPU. If you are using your own seafloor, water box, and gobo, then it may be a matter of adjusting the tiling scale of the caustic image maps to fit your models. If you have not yet downloaded the undersea godray kit linked in my previous post, try using that.

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