I've never seen water simulation with this degree of complexity in games. I've seen it in prerendered video sequences, but when you sit and look at a lake or river in an Elder Scrolls game (or similar), it is usually much more simplified -- or has a flow which is modeled to look pretty.

The difference here is that it's showing interaction between the water particles and things that they impact on: characters, boundaries, piers, and behave in a more realistic way than games have previously had.