Catalina 6 is a US Navy PBY-4 Catalina, one of the Patrol Wing 10 aircraft identified as No. 4 or No. 8, and it is the best-preserved of the American flying boats in the harbour. It is also the one site on DSAC's list that divers cannot visit. Darwin Harbour was a major flying-boat base during the Second World War. US Navy Patrol Wing 10 PBYs were moored in the harbour when the Japanese attacked on 19 February 1942, and from 1944 the RAAF operated Catalina squadrons from the harbour on long-range minelaying and patrol missions into the Netherlands East Indies. At least three RAAF and six US Navy Catalinas were lost in the harbour, and DSAC numbers the known wrecks Catalina 1 to 6. The PBY Catalina had a 31.7 m wingspan, a 19.4 m hull and an empty weight of about 9,500 kg, so even a broken wreck covers a surprising area of seabed. The NT Government lists Catalina 6 alongside the Booya as the two Darwin Harbour sites with closed-waters controls, and DSAC notes that the site still has a heritage restriction zone in place with no entry.

From DSAC's description the forward section is still clearly visible and the wings are intact but flipped upside down, with the engines facing the rear; the rest of the aft fuselage has either burnt out or is covered in mud. The inverted wings suggest the aircraft rolled as it sank after being set alight. DSAC records the depth as 12 m and lists the loss year as 1945, which, as with its sister aircraft, conflicts with its loss in the 1942 raids. The site is included here so that divers know it exists and know to stay out: the protection exists because it is the most intact example of its kind in the harbour and a key piece of evidence about the first raid. Anyone with research interest should approach the Heritage Branch.

Not accessible. Catalina 6 lies within a declared heritage restriction zone in Darwin Harbour with closed-waters controls - entry to the zone is not permitted without a permit from the NT Heritage Branch, which is normally granted only for research and management. The general harbour launch points are Cullen Bay, the Stokes Hill / Frances Bay ramp and East Arm ramp, but recreational divers should not attempt to visit.

Contact the Heritage Branch on 08 8999 5039 for information.

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.

Not available for recreational diving. Permitted research dives are planned by the NT Heritage Branch.

No operator access - closed heritage zone. Research dives only, by or with the NT Heritage Branch.