Occlusion Culling - Why do non-static objects disappear?

Hi,

I have a scene with a submarine full of objects and rooms, all static. The occlusion areas are only inside the sub.

However, Umbra culls the exterior when I walk outside (the dock too), which are NOT static.

Can it be that occlusion culling is only good for big outside environments ?

there is also dynamic occlusion culling which here might trigger in.

also there is general culling

deactivate non static objects in the scene and after the occlusion culling activate the objects then it will there.