My BP_FluidSim01 also doesn’t do anything.
Probably need to wait for the next release (or two) for improvements seeing as the water system is still a work in progress.
The foam ‘kinda’ works if you use specific water material settings:
https://forums.unrealengine.com/development-discussion/rendering/1840270-unreal-4-26-ocean-foam?p=1851940#post1851940
However, I can’t quite get it to look as good as shown in the UE live stream:
Keep playing with the water foam params.
It’s possible that there’s a specific combination of values required to get a good effect.