The approach to Marsden Point has a shallowest depth of 14.6m at chart datum between the Fairway Buoy and No 1 buoy. The least width of 190m is between No 3 and No. 6 buoys. Tidal streams are strongest in the area of No. 7 buoy where rates of over 3 knots may be experienced.
For vessels proceeding to Northport from 0-390m, the controlling depth is 13m at chart datum and from 390-570m it is 14.5m. The swinging basin has a maximum width of 400m. For vessels proceeding to Northport Marsden Point Jetty berth, the controlling depth is 7.1m at chart datum.
From One Tree Point up to Whangarei the channel is shallower and narrower with a charted channel minimum depth at chart datum of 7.0m. The minimum width for most of its length is 90m.
The minimum charted depth to Portland is 4.7m at chart datum.