There are a couple ways to do this.
First thing you can try is use the custom water.
All it is is a simple plane that you can add the waves assets too.
I would suggest adding a plane with more subdivisions because the standard plane is not dense enough for decent waves.
The best thing to do but also more complicated is make a change to 2 of the materials used by the water brush manager. But it would allow you to keep the landscape under it and use the far water meshes.
1: On the landscape_waterbrushmanager scroll down to find the top 2 materials, brush angle falloff, brush width falloff. duplicate those.
2: open the material duplicates and change the output from unpack to pack, basically not using the landscape deform operations( image provided to show what it needs to be)
3: switch out those in your water brush manager to the new ones.
4: after dragging in the water body ocean, select the spline points of the island, drag them up a bit.
5: click the “select all spline points” options and simply set their locations to 0,0,0.
6: you should now have the ocean without the islands. Select the WaterZone object and find the far distance mesh extent. increasing that will give you distant water to fill in the horizon.
That should give you the scene you wanted
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.