By Michelle Saffer
(This article was published in the False Bay Echo and is republished with permission. The survey photos are the property of Underwater Surveys.)
29 Nov 2012
The False Bay seabed is revealing its secrets thanks to high-tech underwater surveys. The precise outlines of wrecks off Glencairn to Cape Point were shown to the Fish Hoek Historical Society, showing that one of the wrecks may have been stripped.
Because no one has come forward to pay for the wrecks to be surveyed, Mark Prowse, an oceanographer with the Capricorn Park business Underwater Surveys, manages to arrange his equipment tests over where the wrecks are.
Their survey vessel, a 6.7 custom-fitted catamaran, uses a multi-beam sounder with a laser that sprays a thin line of soundings, said Mr Prowse. There are 240 soundings each time the laser goes “ping”, meaning that each “ping” gets 240 points, leading to an extremely accurate three-dimensional model. Motions sensors ensure that each point is accurately positioned on the earth’s surface.
During his talk earlier this month, Mr Prowse demonstrated how the soundings are turned into 3D models that can be rotated to enable the underwater surfaces – in this case the wrecks – to be seen in a way they have never been seen before.
Mr Prowse said it was “scary” how little was known about the wrecks. A rectangular wreck off Glencairn is known as a cement barge, but various sources disagree as to what the wreck is. Some sources say the wreck had been used to transport stones from the Glencairn quarry, but other sources say that stones were never transported from the quarry by barges.
While Mr Prowse was testing their equipment and conveniently mapping the “barge”, he found “large block-shaped objects lying on the sea-bed, 318m from wreck.
“They could they be dressed stones from the quarry,” said Mr Prowse.
Another wreck he had surveyed were the Brunswick, an English East-Indiaman which ran aground in 1805. “She was of wooden construction and all that remains now are sections of her hull timbers and some copper sheeting that used to cover the timber,” said Mr Prowse.
Perhaps the most poignant of the wrecks surveyed is SAS Pietermaritzburg, fondly known as the PMB and originally the British mining ship HMS Pelorus that led the D-day invasion of Normandy in 1944, in World War II.
According to research by the South African Naval Heritage Trust and the Simon’s Town Historical Society, the ship was built by a family firm on the River Clyde in Renfrew, Scotland. It was launched in 1943 and named after a dolphin, Pelorus Jack, that used to escort ships in the Cook Strait off New Zealand in the late 1800s.
When the Allies decided to invade German-occupied France, the HMS Pelorus was the lead ship in the convoy, ensuring that the pass was swept clear of mines. It was not an easy task, with most of it done in the dark in a narrow channel, where it was difficult to manoeuvre, under fire from enemy aircraft. Once they had neared France, their job was to anchor and act as decoys.
“If necessary, we were to be sacrificed, drawing [the German’s] fire so that the [Allied] battleships could get them before the troops were landed,” one of the crew members wrote later.
“After we had swept our channels during the night, and had been at anchor off the beach, I never heard such sweet music as when the cable started rattling, bringing up the anchor at 0730, as we turned for home.”
The HMS Pelorus was “adopted” by actress Vivien Leigh who was famous for her role in “Gone With the Wind”. When the ship was sold to the South African navy in 1947, Vivien Leigh came to say farewell.
The ship, renamed the SAS Pietermaritzburg, was used as a training ship and, at the end of its life in 1991, as an accommodation ship.
There were only two ships in this class of the 98 built left in the world and great efforts in South Africa and abroad went to try to save the ship as a maritime museum. This failed and the ship was scuttled with military honours off Millers Point in 1994, with many of those who tried so hard to save the ship watching from the shore.
Since then, there have been reports of a salvor stripping the ship (“Salvor ‘stripping’ wreck”, Echo July 26) and Mr Prowse’s two surveys, one in 2003 and the other in 2012, would seem to indicate this has been the case.
Mr Prows said that his 2012 survey showed that “there is almost nothing left. The entire superstructure has gone and the hull is deformed”.
Eric Mawhinney of the Simon’s Town Historical Society said the society had applied to the SA Heritage Association to have the ship protected under the National Heritage Act.
“We wouldn’t expect [the ship] to last for ever, but we are concerned about it being destroyed. It is a very special ship,” said Mr Mawhinney.
He said the society was waiting for the outcome of its application.