One option might be to put the water bodies in separate streamable levels, and only stream in the ones that are close to the player, if the 8x8 solution isn’t enough.
It’s hard to make abutting water bodies look good though, it wants each contiguous surface to be a single thing. (At least when I tried it, which was a while back)
Unfortunately, this won’t help because the problem is in the editor where there isn’t anything “close to the player”. And because of the Unreal bug, one cannot unload parts of the landscape when it contains water bodies.
offtopic territory: i’m not aware of a “water plugin”. i tried some other setups in 5.0, iirc. some sim and tesselation stuff. alil bit more compute intensive. can’t remember how it performed or how much memory it consumed. was not kilometers of water in the first place. large dense meshes that are not procedural will always feast on vram tho. yep
The Unreal terrain water system (with water flow, etc) started life as an EPIC plugin. It might be it’s just standard now, or at least auto-enabled? Haven’t checked in a while.