Hey there @anonymous_user_e7fdc89d1! Welcome to the community! So every component in the water system affects terrain to an extent. When you first drag out an ocean it makes an island spline to start out with. It will adjust the default terrain layer and effectively destroy any sculpting you’ve done on those locations. It’s usually best to begin sculpting on a different layer. This allows your changes not to be shifted by the water’s height map changes.
Did you hide the water for the screenshot or is it not there at all?