I resolved the issue. I figured it looked like z-fighting, even though there is nothing there for the plane to intersect with. For whatever reason moving the plane from z = 0 to anything else completely stops the buggy effect. I figured 0 would be a good height for the water in my game, but I guess for now I’ll call this fixed.
Still not sure why this is happening, as my terrain is at height level 100 and also sculpted down much further.