The Birchgrove Park is Sydney's most intact deep shipwreck and one of its most poignant. Built by J. Lewis and Sons at Aberdeen and launched in November 1930, she was a 47 m, 640-ton steel collier for R.

W. Miller and Co, designed for the Newcastle-to-Sydney coal run. Requisitioned in 1941 as HMAS Birchgrove Park, she served the Navy as an auxiliary minesweeper and stores carrier in New Guinea before returning to Miller's in 1946.

At 2.45 am on 2 August 1956, running south from Newcastle with a full cargo, she was caught by a southerly buster; water entered through corroded pipes and loose hatch tarpaulins, she listed heavily and capsized. Ten of the crew died, two never found, and the subsequent inquiry became a landmark in Australian maritime safety. The wreck was located in 1965 by Wally Gibbins and Ken Bateman.

She lies on her port side facing west in 51 m, standing about 4 m above the sand. Although the hull has broken around the boiler section and the bow has separated, the ship is still recognisably a ship: the bridge lies detached but enterable on two levels, the forecastle can be entered with several ways out, the mast and a crane arm lie across the sand, and the boiler, engine, propeller and rudder are all in place. Conger and moray eels live in the boiler tubes and wobbegongs are sometimes found in the firebox.

Large schools of fish gather over the hull, and the debris field runs west into the sand. Current is generally slight this far off the coast, and visibility is often good, though Hawkesbury River floods can turn the water brown for days. It is strictly a dive for experienced, well-equipped decompression divers: 51 m is deep for air, the site is remote, and the wreck's compartments are silty.

For those qualified it is the finest example of an intact collier in the Sydney area and a war grave-like memorial to the last major coastal collier loss on this coast.

Boat only, roughly 8 km south-east of Barrenjoey and 4.5 km off Whale Beach. Private boats and tech charters launch from the Pittwater ramps (Bayview, Careel Bay, Akuna Bay) and run out through the Broken Bay entrance (about 30–40 minutes), or from Roseville Bridge/Rose Bay and run 60–75 minutes north. The wreck rises only 4 m off flat sand, so GPS and a sounder are needed and the shot must land on structure.

A drifting deco station and a boat handler who stays with the divers are standard.

Open ocean off Broken Bay. Exposed to every swell direction except due west; look for less than 1.5 m swell and light winds, ideally a morning westerly before the north-easter fills in. Hawkesbury River flood plumes after heavy rain cut visibility badly for days.

Tidal streams in and out of Broken Bay can be felt on the shallower sites near Barrenjoey; the deeper offshore wrecks see East Australian Current surface streams instead. Best visibility May–September.

Descend to the high side of the hull at 47 m. Tour the detached bridge (upper and lower levels), the forecastle with its several exit holes, the mast and crane arm, then the boiler and engine section to the prop and rudder. Turn on gas, return to the shot, and run staged decompression; keep an eye out for whalers at the shallow stops.

Trimix strongly recommended (END limits); typical 20 minutes bottom time with 40+ minutes deco on 50%/100%. Reel and line for bridge/forecastle penetration; twinset or CCR with bailout. Protected historic shipwreck – nothing may be removed.

No scheduled recreational charters. Sydney Dive Charters (Rose Bay/Manly) runs technical charters to the Birchgrove Park on demand for T1/Tec45+ certified divers; otherwise private boats and technical dive clubs launching from Roseville, Akuna Bay or Rose Bay ramps. Expect a handful of visits per year.