Hi! it has been a while since i last tried it so im not sure to what degree it still works on newer versions of the engine. The “landscape under it” referred to being able to have an ocean with a landscape under the water, without having the ocean splines themselves modify the landscape(like adding an island) If in your case you dont want any landscape at all under the water you can try the custom water as i explained in the top part. have to retry the water stuff in recent ue versions to see if anything else might work. 