Here is the progress ive made of the modeling, just about there i think. There could be more detailing, but the for idea I had, with the distance and underwater fogging effects, i think it will work ok. Hopefuly have it textured for this weekend.
Also included is a ref i found on google, this is the type of look im after. So lots of nice volumes, and debris/particles in the water.
These are the passes i was thinking of. Top water (raytraced), Water Fog, Volumes, Particles/Debris, Shark beauty (+ specs, reflection, AO etc), Shark water caustics and shark depth pass.