The normal direction of approach is from the northwest, passing west and south of Bathurst and Melville Islands, which form the northern side of Beagle Gulf. Clarence Strait, which usually requires local knowledge, leads to the east of these islands and saves about half a day for vessels bound to or from eastward. Clarence Strait has a minimum depth of 23 ft (7 m).

The Entrance Channel for the Port of Darwin is between Charles Point Patches and Middle Ground through Middle Pass (12°21'S 130°43'E). Middle Pass is a light-buoyed channel with a charted depth of 40 ft (12.2 m). Middle Pass is marked for vessels whose draft exceeds 29.5 ft (9 m). Ships drawing more than 36.1 ft (11 m) may need to wait for appropriate tidal conditions before entering the Port of Darwin. Vessels up to 804 ft (245 m) in length, with drafts up to 39.4 ft (12 m), are generally the maximum. As the vessel proceeds down the channel between East and West Points, the reefs reduce the navigational entrance to a width of about 1 nmi (Hydrographic Service, 1992).

Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/australi/darwin/text/sect3.htm