This is an effect thats more for compositing than anything in fact, as a visual effects artist, this would be a much simpler and is a much more effective way of doing it.

The catch is you will have to have 2 ocean shaders, pick a frame where the ocean is going to be frozen, and then make the entire frozen ocean static by putting the Wind Speed at 0, then all you have to do is texture your ocean which will be the hardest part of tweaking it....

then use after effects or shake and composite the two together... in shake you can use a rotoshape and/or quickpaint and animate curves to make a freezing motion and then just fix up the look using color correction and other sorts....

I know it sounds long, but that will be much easier unless you're a hard core MEL scripter and can query different points in the ocean...which is very very possible, but much more lengthy than what I mentioned...

I will say this, based on my experience, it can get VERY expensive turning fluids into polygons and adding the refracting shader in, especially if you are trying to pull this effect off....