If you select Moonpool and build one, the resulting moonpool isn’t big enough to fit a vehicle dock. This is a base-level quality of life failure. Adjust one or the other. A moonpool that can’t fit a vehicle dock is not meeting its basic requirement. Don’t inflict this annoyance on the typical end-user if you can avoid doing so.
Apparently this was caused by the ceiling lights having collision which interferes with the vehicle dock.