Put simply, they avoided raytracing, and used very customized shaders with reflection maps and fresnel ramps for the effect. Then rendered the scenes in render passes (not easily accomplished in Poser, and some types of passes are not possible) to add the final FX as video postwork (Flame and Inferno are high-end video fx compositing tools, which are often used to put together multiple render passes from 3d software, and add some incredible effects to them). Without using postwork in apps such as AfterEffects or Combustion, you could still get this effect in Poser, but you're looking at long render times which will involve raytracing. If you have a video FX editor, you can render this out in 'simple' passes (character as one pass, then the "water" as the other, and if you have P6, shadows can be your third pass), using animated nodes and reflection maps in P5/P6 (no raytracing), then add the ripple effects and pseudo-reflections in post. Ajax has a good water shader in his materials pack for P5 which can be tweaked.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.