Hopper Barge 656 is one of a cluster of unpowered dump barges that the NSW Maritime Services Board sank on the Long Reef artificial reef ground in the late 1970s and 1980s once they were no longer needed for carrying dredge spoil out of Sydney Harbour and Botany Bay. Sydney Dive Charters, which lists it among its ten Sydney technical wrecks, gives it as about 50 m long, lying 3 nautical miles offshore in 45–51 m, 'largely intact' but with deck plating that is deteriorating, and notes that the bow void is easily accessible to technical divers. Like the Apollo Barge and the Canoe Barge it is a box-section steel hull with a blunt bow, an anchor winch, a row of hopper bays with bottom doors, and small machinery and crew spaces aft; the number 656 was its fleet designation.

The dive is one of structure rather than history. On the deck at 45 m the hopper openings and door gear can be examined, and the hull sides drop to sand at 50–51 m where the plating is beginning to rust through, letting light into the holds. Fish life in the Long Reef barges is concentrated in the holds and voids – jewfish, bastard trumpeter, bullseyes and nannygai – with kingfish over the top, and the outside plating carries sponges and jewel anemones.

Visibility this far out is usually 15–25 m. It is a decompression dive requiring trimix or careful nitrox planning, a shot line placed on the wreck, and a drifting deco station, and it is normally dived by teams that already know the Dee Why and Coolooli and want the rest of the reef ground. Michael McFadyen's No Frills Hopper Barge, sometimes confused with this site, lies off Royal National Park and is a different vessel.

Barge 656 suits qualified technical divers on a Sydney Dive Charters Tec 1 day; the operator's site is the only published description and the position is not public.

Boat only. Technical charters and private boats launch from Roseville Bridge (Middle Harbour), Rose Bay or Little Manly and run 45–60 minutes north past Dee Why to the Long Reef artificial reef ground 4–6 km offshore, or from the Pittwater ramps/Careel Bay Marina and run 40 minutes south around Barrenjoey. The barges lie on a flat sand plain and can only be found by GPS and sounder; the shot must be dropped on the structure.

Drifting decompression station with a following boat.

Open water 4–6 km offshore with no lee: swell over 1.5 m or wind over 15 knots from any direction makes the shot and the long deco hang unsafe, and surface current from the East Australian Current can run hard while the bottom is still. Best visibility (15–25 m) from May to September; summer brings warm surface water, plankton and a thermocline. Avoid the days after heavy rain when the lagoon outflows dirty the inshore layer.

Descend the shot to the deck at about 45 m, tour the deck plating and hopper openings, look into the bow void (the easiest access point), then circuit the hull on the sand at 50–51 m and return to the shot for staged decompression.

Decompression dive: trimix or air/EANx with 50%/100% deco gases, 20 minutes bottom time for 30–50 minutes of stops; twinset or CCR with bailout; reel and line for any penetration; silt inside holds. Sydney Dive Charters requires Tec 40/T1 and 100 logged dives.

Sydney Dive Charters – Tec 1 charters (Thursday/Sunday programme from Little Manly ramp, Rose Bay wharf or Careel Bay Marina) on demand; otherwise private boats and technical dive clubs. A few visits a year.