So I tried this from two directions using the water plugin. Both attempts kind of failed at least if I’m being super nitpicky about it.
Approach 1, River Body:
This looks quite alright. The only thing I was missing was some more waves, bc the rivers are apparently being created with normal maps only. Also I’m kinda concerned, whether the water level could be changed ingame on a river body, which I wanted to do later.
However for the waves I noticed that I could switch on different parameters from all water systems. I switched on the waves, but I didn’t get any options for those in the details.
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Approach 2, Custom water body:
As you can see I managed to get bigger waves on this one. I first tried to give the waves a direction, but there was no way of adjusting the speed to make it really seem raging. then I noticed I could switch on the river parameter for this, which I did, as you can see, but the rivers direction does not go along with my object, as you can see. And this time, I’ve seen no way to customize that either.
Approach 3?
So I dunno how performant these water bodies are in a game anyways, but I’m sure this could be done a different way too using a plane and throwing a noise/cloud texture on it to animate the topology.
I did this very quickly in Blender:
Just so you get the idea. I would’ve no clue how to animate this, but I’m sure it’s possible.
edit: I just noticed, there is an Ocean Modifier in Blender, certainly that could be useful. 