Ships lose anchors. It happens often enough that there is a routine for it. Ships do not lose propellers. When the owners of a coal carrier told us theirs had sheared off its shaft near the Hay Point anchorage, about five nautical miles off the coast, we asked around. Nobody in the project team, the owners' office or the salvage trade had heard of it either.
Finding it
The first job was the same as for an anchor: cover the ground with side-scan sonar. We towed the Klein 3000 towfish in a grid over the anchorage until a target showed up with the right size and the right shadow, then put divers on it to confirm. It was the propeller, lying in about 20 metres of water: 6.5 metres across, 2 metres tall, 17.5 tonnes of bronze.
Planning the lift
A salvage like this is mostly arithmetic and preparation. You start from the weight and the dimensions and work out what will lift it safely: how many lift bags, what size, whether to float it or lift it hydraulically, how to rig spreader bars so the blades are not loaded in a way they were never designed for. We spent far longer on that than on the dive itself.
On the day, a team of nearly fifteen people was on the water: divers, a dive supervisor, the skipper, crane and tug operators. The divers went down, rigged the propeller, inflated the bags and floated it off the bottom. The tug then towed the whole package back to Hay Point, where it was lifted onto hardstand.
"It sure was impressive to bring up a propeller like that," our director Ed Korber told the Daily Mercury at the time.
Where it went next
From the holding yard at Hay Point the propeller travelled by low loader, with a police escort, to the North Queensland Bulk Ports facility at Mackay Harbour. A 70-metre tug out of Singapore collected it from there, bound for the Philippines, where the owners planned to reuse it. Before it left, the shaft end was sent for metallurgical testing to understand why it had failed.
And two anchors
The same sonar and the same crew recovered two ship anchors of around 12 tonnes each from that stretch of coast, one of them over the Christmas period. One of those anchors now sits on a roundabout at Mackay Harbour. People drive past it every day without knowing that it spent months on the seabed first.