I just started working with Unreal Engine this past week and ran into this same issue. The fix in the video listed here did not work for me for whatever reason. However I did find something that did work and I’ll share some screenshots to help explain. I specifically used the ocean body of water so I can’t verify if this will work for other types.
Under the waterbodyocean item go to the details and look for the terrain tab and uncheck the Affects Landscape option.
Doing this is what fixed it for me and I could adjust the water without the spline comp outline distorting my landscape.
