There’s a bunch of stuff to read and learn about, HLODs, the distance in your World Partition settings you are rendering actors, actor default visibility and datalayer default visibility when you load in. I haven’t played with that Water plugin yet. How are the rivers generated, are they a mesh/particle effect actor placed somewhere? Maybe wherever the “source” of the river is needs to be loaded on the World Partition? Just guesses here. Glad you’ve got some progress!