The spokesman said fixed-window arrangements are normally in place for container shipping services, but due to vessel schedule unreliability, all berth windows are suspended at Napier Port.
Container vessels will be worked on a "first to pilot station, first to work" basis until further notice.
The anchored ships are the NYK Futago, IVS Merlion, Rio Blanco, Bomar Resilient, Neokastro, Kota Lembah and Rio Bravo.
The NYK Futago ship is due to depart the soonest, at 8pm on June 1, while the Rio Bravo container ship has an estimated departure time of 8.30am on June 7.
Napier Port uses a Dynamic Under Keel Clearance system to determine when it is safe to bring a vessel into port.
The system integrates real-time measurement of tide height and waves with modelled vessel motions to determine if a proposed transit for a particular vessel meets predetermined under-keel clearance safety criteria.
Operational parameters are also considered in the port's protocol as ships with a shallower draft may be able to come in safely ahead of ones with a deeper draft that may need to wait for swells to decrease further.