I modelled a couple of rocks, crafted a quick sort-of icy material (see below) and used a particle system to generate fields of ice-rocks. I added a single plane for the water level, and extruded a bit of a weird shape to form the basis of some block for a half-frozen Shiva.
If you look at the bottom most image in this post, you'll see how the particle systems where just emitting these rocks from plans underneath the water level. Pretty ugly, but hey, if it works.. :)