Floating dock (impounded)
A floating dock, floating harbour or wet dock is a dock alongside a tidal waterway which maintains a 'constant' level, despite the changing tides. == Operation == At the most basic level, a floating dock is isolated from tidal water by a lock gate, at least, although in many dock systems the entrance is more complex than this.
Source: Wikipedia — Floating dock (impounded) (CC BY-SA 4.0)