The Medkhanun 3 is a steel fishing vessel of 25-30 m that was apprehended for illegally fishing in Northern Territory waters and forfeited. Instead of being broken up, it was cleaned with funding from ConocoPhillips through the Darwin Amateur Fishermen's Association and scuttled to extend the existing reef formed by the refugee boats. Between 1976 and 1981 more than 50 boats carrying Vietnamese refugees reached Australia's northern coast, most of them arriving in Darwin Harbour. Several of the steel boats were later cleaned and scuttled west of Cullen Bay together with a redundant construction barge to create a fishing and diving reef, and the site was extended in later years with a confiscated illegal fishing boat. The group sits in 20-25 m within a few hundred metres, and some operators have linked the wrecks with rope so that more than one can be visited on a dive.

The Medkhanun lies intact on its port side in about 18-20 m, making it the shallowest of the group. Because it is the most recent addition, the structure is still sharp and recognisable: open forward holds that can be viewed with a torch, a wheelhouse and crew quarters that can be looked into through the doors and windows, and deck fittings still in place. Silt has settled thickly inside and can reduce visibility to virtually nothing if disturbed, so it is a wreck to observe from outside. Fish colonised it quickly, and NT Fisheries lists jewfish, snapper, cod and Spanish flag here. It offers a good contrast with the older, heavily encrusted refugee boats nearby and is a sensible second dive after one of the deeper wrecks in the complex.

Boat only. The refugee-boat complex lies in the outer harbour a short run west of Cullen Bay - typically 10-15 minutes from Cullen Bay Marina or the Cullen Bay public ramp (off Marina Boulevard, trailer parking on site). NT Fisheries publishes the positions of each wreck for anglers, so expect fishing boats on the marks on neap weekends.

Drop a shot beside, not into, the structure, and plan to be on site before high-water slack; the complex is exposed to the full tidal flow once the tide turns.

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.

Descend on the NT Fisheries mark to the hull lying on its port side. Swim along the exposed deck, look into the open forward holds with a torch, peer through the wheelhouse and crew-quarters windows, then return along the keel. Do not enter - one fin kick can drop visibility to nothing.

Ascend on the shot.

Darwin Dive Centre and Dive Darwin include the Vietnamese refugee boats and artificial-reef wrecks in their neap-tide harbour charters; Darwin Sub Aqua Club dives them regularly on club days. No fixed daily schedule - trips follow the neap cycle.