Zealandia was a well-known Australian ship long before she became a wreck. Built in 1910 by John Brown and Company at Clydebank for Huddart Parker of Melbourne, the 125 m, 6,600-ton twin-screw liner ran the coastal and trans-Tasman passenger trade, served as a troopship in the First World War, and was chartered again by the Department of Defence in 1940, carrying units of the 8th Division. On 19 February 1942 she was at anchor when bombs fell close alongside and one went down a hatch into No. 3 hold, damaging bulkheads and holing the starboard quarter.

Strafing disabled her fire pumps, the fire reached ammunition in the hold, and the master ordered her abandoned. Two or three of her crew of about 145 were killed. She settled slowly with her masts showing above water.

The 19 February 1942 raids - two waves of Japanese carrier and land-based aircraft, the first and heaviest attack ever made on mainland Australia - sank eight ships in the harbour and killed more than 230 people. In 1959-60 the Japanese firm Fujita Salvage cut most of the wrecks down to or below the waterline for scrap, so what divers find today is usually the lower hull, machinery that was too heavy to lift, and the cargo that the salvors were not permitted to remove. Zealandia was salvaged in 1960 and scrap from her was reputedly used to cast 77 bronze crosses for a church in Japan.

What remains in 18-22 m is a jumble of hull structure and cargo on the bottom, and it is the most colourful of the raid wrecks: soft corals cover much of the steel and fish life is consistently good. It is an easy wreck to combine with the Meigs, Mauna Loa or British Motorist over a neap-tide weekend, and a good second dive for divers comfortable in low visibility.

Boat only. Darwin's charter operators leave from Cullen Bay Marina or the Darwin Waterfront precinct and run across the harbour to the site in well under half an hour on a calm neap-tide morning. Private boats can launch at the Cullen Bay public ramp (west of the CBD off Marina Boulevard), the Stokes Hill / Frances Bay ramp beside the Waterfront, or the East Arm ramp for the southern anchorage.

Mark the position on GPS before the dive - the wrecks lie in open water with no surface marker - and drop a shot rather than anchoring into protected structure. Parking and trailer bays are at all three ramps; air fills and hire through the Darwin dive shops.

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 at neap slack, then follow the lower hull and scattered structure, looking under plates for cod and around the soft-coral covered pieces. Hold 18-20 m, turn at half gas and navigate back to the shot for the ascent.

Darwin Dive Centre and Dive Darwin run harbour wreck charters only on neap-tide windows (typically a few days either side of each neap, weekends favoured); Darwin Sub Aqua Club dives it on club neap-tide days (members plan dives at Thursday meetings at the Darwin Ski Club). No daily schedule.