The Betsey Island graveyard, west of Little Betsey Island at the mouth of the Derwent, is Hobart's ships' graveyard: from the 1930s to the 1980s obsolete vessels, barges and sections of the old floating bridge were towed here and scuttled in about 20-34 m. The Marine Life Network guide calls it a huge concentration of wreck dives very close to Hobart, with a pebble-and-mud bottom that stirs up easily, poor visibility after bad weather or decaying Storm Bay swell, and massive yellow and white jewel anemones and, at times, hordes of school fish on the wrecks. The Swiftness was built in Scotland in 1920 and scuttled at Betsey Island in 1979.

The guide gives her as 147 tons and 98.4 ft (30 m) long. She lies about 100 m south-west of the Macquarie in about 20 m. The hull is heavily broken, but parts of the bow and stern remain intact, and her most unusual feature is her steam engine, which the guide notes came from a former mainland mine plant rather than being purpose-built for the ship.

The engine block and associated machinery stand up from the wreckage and are a focus for photographers when visibility allows. Jewel anemones, sponges and sea squirts cover the steel, and fish shelter in the broken hull. Because she is close to the Macquarie and the barges, experienced divers can visit her as part of a multi-wreck dive using a compass bearing – but only in reasonable visibility, as the bottom is featureless between wrecks and silt clouds easily.

Otherwise, shot her directly. The Swiftness is a good example of the practical, make-do engineering of Tasmania's small coastal and harbour vessels in the twentieth century.

South Arm is about 35 km (40 minutes) south-east of Hobart: cross the Tasman Bridge, follow the South Arm Highway (B33) through Rokeby and Lauderdale to South Arm. The main boat ramp is at South Arm (Blessington Street/Harbour area) with trailer parking and toilets; Lauderdale (Doran's Road) is an alternative ramp further north. From South Arm the Betsey Island graveyard lies about 5-6 km south-east across the mouth of the Derwent, west of Little Betsey Island, roughly 15-20 minutes by boat.

The Marine Life Network guide recommends an echo sounder to locate the individual wrecks, which are low on the bottom; there are no public moorings, so anchor carefully in the pebble-mud bottom off the wreck and leave a boat attendant.

Betsey Island lies at the mouth of the Derwent where it meets Storm Bay, so decaying southerly swell and strong southerly or south-westerly winds make the ride rough and stir up the pebble-and-mud bottom. The Marine Life Network notes the graveyard is not renowned for visibility and recommends calm, dry weather and an ebb tide, when clearer water sits over the wrecks. After Derwent floods the water can be very dark.

Northerly and light westerly winds give the best conditions; late summer and autumn are most reliable. Expect 3-8 m visibility at best, often less.

Swim a compass bearing south-west from the Macquarie (about 100 m) or shot the Swiftness directly; examine the steam engine and the surviving bow and stern sections, then return to the shot.

No scheduled operator trips; Hobart clubs (Tasmanian Scuba Diving Club and others) and private boats from South Arm and Lauderdale. The Dive Shop Hobart and Go Dive Tasmania can advise.