Sunk in 2002, ex-HMAS Hobart Now Teems With 50 Fish Species

A survey 18 years after the ex-HMAS Hobart was scuttled off South Australia found the warship wreck hosting more than 50 fish species.

A 134-metre guided-missile destroyer that Australian authorities deliberately sent to the bottom of Yankalilla Bay has grown into one of South Australia's richest marine habitats in under two decades. Resting 30 metres down, the ex-HMAS Hobart was scuttled on 5 November 2002 and slipped beneath the surface in two minutes and 17 seconds after controlled charges fired along its hull, the Naval Historical Society of Australia records.

A scientific survey conducted 18 years after the sinking counted more than 50 fish species living on and around the wreck, together with dense colonies of filter-feeding organisms. The results appear in reports from South Australia's Department for Environment and Water (DEW), which cite the site as evidence that retired military ships can seed marine life across stretches of seabed that offer little natural shelter.

From Vietnam veteran to sunken reef

The Defoe Shipbuilding Company in Michigan, in the United States, built the vessel, and it joined the Royal Australian Navy in December 1965. Over more than 35 years, the destroyer served three combat tours during the Vietnam War before it was retired from service in May 2000. The Australian Department of Defence then handed the ship to the state of South Australia.

Preparing a warship for the seabed took careful work. The Fleurieu Artificial Reef Society, working with state agencies, stripped out hazardous materials, drained the last of the fuel and cut openings so divers could later move through the hull. When the charges detonated off the Fleurieu Peninsula, the destroyer settled upright on a flat, sandy floor almost bare of rocky ground.

That sudden vertical structure changed everything for local sea life. Gun turrets, decks and open engine spaces rose above the sand and disrupted nutrient-rich coastal currents flowing past. Sponges, barnacles and soft corals took hold on the steel, turning the hull into a foundation for a growing food web.

What the survey found

The Marine Science team at DEW carried out the biodiversity count using the standardised Reef Life Survey method of underwater visual census. Divers logged snapper, southern blue devil fish, bullseyes and leatherjackets sheltering among the plates. The metal panels break up strong tidal flows and shield smaller fish from predators, forming pockets of habitat at varying depths through the wreck.

Legal protection has helped the colony thrive. The Hobart lies inside the Rapid Head Sanctuary Zone within Encounter Marine Park, where both commercial and recreational fishing are prohibited. DEW management guides say rangers patrol the zone to uphold the no-take rules, letting fish stocks and encrusting organisms build up free from fishing pressure.

A magnet for divers

Beyond its conservation value, the ship has become a leading draw for experienced divers who seek out cold-water wrecks. It stands apart from most of Australia's sunken naval reefs because divers can enter parts of the interior under regulated access, including the original engine room and the areas that once held missiles.

The Hobart is not alone. Australia has scuttled other warships for the same mix of habitat creation and tourism, among them the ex-HMAS Adelaide off New South Wales and the ex-HMAS Canberra off Victoria. Research published in journals such as Ecological Engineering and Frontiers in Marine Science reports that carefully managed steel wrecks can carry fish numbers and species variety comparable to nearby natural rocky reefs.

By converting decommissioned vessels into lasting reefs, environmental agencies gain permanent marine habitats and a way to offset natural seabed lost along heavily developed coastlines.

ex-HMAS Hobart, artificial reef, Encounter Marine Park, South Australia diving, marine conservation, Royal Australian Navy, shipwreck ecosystem, Yankalilla Bay