I just finished Far Cry 2 today, and in the last mission I saw a waterfall. I analyzed it with the sniper scope of my Dragunov rifle, and it looked basically that it was made out of several emitters. There was one emitter at the start which rotated the sprites to make it look like a swirl. Then there was the actual waterfall emitter, which moved sprites downwards at a higher speed, and at the ending there was a elliptic emitter where the water bounced back from the river once. LE has only one-directional emitters, so you would need to code the elliptic emitter yourself.
I haven't analyzed yet how the waterfalls in Crysis are done, but I think they use a much better approach, as everything in Far Cry 2 was like trying to copy features of Crysis, but failing in basically everything. I was wondering why Far Cry 2 looks so bad, although it had those Crysis style bright and dark areas, but then I noticed it's all fake. Far Cry 2 has no real lights at all, it's all somekind of hardcoded in-place effects. You could see some objects lighted nicely, but everything around them was dark, so there was no real directional light, but only some "light" which was applied on hardcoded objects. Heck, even a plain cube without texture in LE looks better than Far Cry 2