Tasmanian divers have captured remarkable vision of the wreckage of the Lake Illawarra lying at the bottom of the River Derwent, more than 40 years after the ship hit the Tasman Bridge.
Key points:
- The Lake Illawarra sank in 1975 after running into the Tasman Bridge which spans Hobart's River Derwent
- Improved sediment levels have allowed local divers to capture clearer vision
- The footage also shows several sharks and other marine life living amongst the wreckage
The bulk ore carrier sank after striking the bridge in 1975, bringing down two pylons and 127 metres of bridge decking.
Five motorists were killed when they drove into the gap and seven crew members died when the bridge section fell onto the ship's deck.
One body has never been recovered.
For many divers who have visited the wreckage in the past, visibility has been impaired by murky conditions.
But the new vision clearly shows the wreckage and an abundance of marine life, including several sharks.
'We're able to see more and more'
Tasmanian University Dive Club secretary Andrew Bain, who posted the vision on social media, said the River Derwent's water quality had improved during the group's last few dives.
"The visibility in the Derwent has improved for us [the divers] over the years … so we've been able to see more and more," he said.
"We can look up at the bridge of the boat and we can see all of the bridge from the bottom of the hull, and that's such an amazing view to see."
He said there were two dive sites, the site of the wreck itself and another where the bulk of the bridge had fallen.
"[The bridge] is an amazing place for animals to grow and fish to live inside," he said.
"We have the old railings pointing up into the ocean and the roadway with its white markings are still visible."
He said there was plenty of marine life, including a population of sevengill sharks.
"Two of [the sharks] in particular we call Pat and Betty and we that we run into on a regular basis," he said.
"They're a lovely, gentle shark … [sevengill sharks] have never been known around the world to harm anybody."
Maritime Museum of Tasmania curator Rona Hollingsworth said it was the clearest vision she had seen.
"Footage from there is often really, really murky because that's just the way it is," she said.
"It is great to have the footage because it is all part of the story of the Lake Illawarra, of what happened and what's still there now."
She said it was important to remember it is a gravesite.
"It is considered a gravesite I believe, therefore divers shouldn't be going anywhere inside it, it's considered sacred, so to speak," she said.
River sediment on the decline
The River Derwent has been beset with pollution problems over the years.
Ursula Taylor, chief executive of the Derwent Estuary Program, said the vision was impressive and reflected what the science has been telling her team.
"It's great to see the fish life and the sharks down there … it's just amazing to be able to see it so clearly," she said.
Ms Taylor said the footage had also confirmed that sediment levels in the Derwent had decreased.
"It's been really great to see in the last couple of years the water sediment levels in the Derwent decline … the science is reflecting the observations of the divers. It's fantastic to see," she said.
"We've been working for a number of years with councils to improve stormwater management in Hobart, which has had a positive impact on the water quality."
Ms Taylor said it was a good opportunity to remind the community that good soil management impacts on water clarity and the health of fish and marine plants.
"One of the original meanings of the name River Derwent actually means clear water … so it's really great to have the river living up to its name," she said.