As you can see, the 3d object is placed flat on the water. This happens when I apply the terrain using the JS code:

const worldTerrain = Cesium.createWorldTerrain()

viewer.terrainProvider = worldTerrain;

(Note: terrains besides water renders fine with this method.)

However, what I am trying to achieve is this:

Unlike the first image, height exists in water and the object is submerged.

I can only get this result by going into the and turning Cesium World Terrain option on.

Shouldn't this be achievable by code? Is this a bug or did I miss something?