Realtime fluid sim is making lots of progress, though full 3D sims still appear to be computationally out of reach, at least for games that aren't focused exclusively on them. Here are some fun fluid sim examples from members of the Ten Minute Physics discord:
I might have to join the discord, that first link is extremely satisfying, and the shading on the materials in the 2nd one does a great of giving the feeling of the 3rd dimension without the computational complexity. Thank you for sharing