HARBOUR ENTRANCE. Strong tidal overfalls may be experienced in the main Channel Entrance north of Stirling Point.  The tidal stream turns 25 to 35 minutes after Bluff High Water and Low Water.  The flood stream continues to flow strongly in the direction of the Entrance Shoal for up to 2 hours after High Water at Bluff.  Tidal stream rates westward of No.2 Beacon may reach 7 knots at extreme spring tides.  Vessels about to enter Bluff Harbour should ascertain whether an outward bound vessel is in the entrance channel by contacting Bluff Harbour Radio.