Mandorah Jetty is the ferry wharf at Mandorah on the Cox Peninsula, on the far side of the harbour from Darwin. marinelife.org.au describes it as a relatively easy dive. Its pylons are covered in sponges, soft corals, ascidians, tube worms and anemones, and larger fish - barramundi, trevally, batfish and groper - lurk among a tangle of long-forgotten rubbish on the bottom beneath the jetty. Darwin's natural reefs are not the clear-water coral gardens of the Great Barrier Reef. The harbour is a macro-tidal, turbid system, and its reefs are low rock platforms and bommies covered in sponges, soft corals, gorgonians, sea whips and hardy hard corals that tolerate silt and big tidal flows. What they lack in visibility they make up for in density of life and the chance of turtles, rays and big fish.

Jetty dives in the Top End are uncommon, and Mandorah is the best documented. The mix of encrusted pylons and junk makes for a good muck-style dive, and the chance of seeing a barramundi in the sea is a local speciality. Depths vary with the tide (the sources give no fixed figure), and the jetty is only practical at high water on a neap, when there is enough depth and the current is slack. Because it is a working ferry berth, diving needs planning to stay clear of ferry movements. The Cyclone Tracy trawler NR Diemen lies about 1.2 km away and the Mandorah Queen is nearby, so a boat trip to the Mandorah side can combine a wreck with the jetty. Mandorah beach is an easy place to wait out a surface interval between dives.

Mandorah is a 15-20 minute ferry ride from Cullen Bay (SeaLink passenger ferry) or about 130 km by road around the harbour via the Cox Peninsula Road. With gear, a private boat from Cullen Bay is most practical. The jetty is an active ferry berth: do not dive in the ferry's approach or while it is berthing, and confirm arrangements with the ferry operator and local authorities.

Enter from the beach beside the jetty or from a boat; keep well away from the berthing face.

Tide is everything in Darwin Harbour: the spring range is 7-8 m and tidal streams run hard through the harbour, so diving is generally only possible on neap tides (range under about 3-4 m), timed to the slack at high water when clearer ocean water sits over the site. Spring tides bring strong currents and silt-laden water with near-zero visibility. The dry season (May-October) gives the most consistent conditions; the south-east trade winds can chop up exposed water in the afternoon, so mornings are best.

In the wet season (November-April) run-off from the rivers and creeks drops visibility, afternoon storms build quickly, and the harbour is in cyclone season; box jellyfish are present October-May.

Dive at high-water slack on a neap. Work along the pylons looking at the encrusting life, then check the rubbish and debris on the bottom under the jetty for bigger fish. Stay under the jetty away from the berthing face and surface at the shore end.

No regular operator; occasional local and club dives on high neap tides.