The tug Jupiter 6 is officially presumed lost with all hands after an emergency radio beacon signal was picked up and a search failed to find the ship.
Several grim signs pointed to the fate of the tug, missing for more than a month.
But they fail to shed light on the mystery of what befell the ill-fated vessel.
The clues are a belated signal from an emergency position indicating radio beacon, a patch of oil and a piece of wreckage in a position about 200 miles south of Port Elizabeth, well off the shipping lanes.
This seems to be the tragic conclusion to the mystery that has haunted the shipping industry since September 6, the day the last communication from the Indian-owned tug was heard.
The tug and her tow were reported missing when no further communications were received and ships at sea were asked to keep a lookout. At the weekend, the tug's emergency beacon finally began signalling and the Maritime Rescue Co-ordination Centre in Bellville sent an SA Air Force long-range aircraft to search the sea around the position signalled by the beacon.
Two ships joined in the search.
The aircraft crew saw only a patch of oil and a piece of wreckage, but no survivors or other signs of the vessel.
Even the wreckage and the oil could not officially be linked to the tug, said a spokesman for the rescue centre who did not wish to be named.
The Jupiter 6 had left Cuba with a scrapped bulk carrier, the Satsang, in tow about three months ago. The two ships were headed for the breakers yards in India, where the Satsang would have been cut up for scrap steel.
They stayed six weeks at Walvis Bay while repairs to the tug's propellers and engine were made, shipping sources said.
After dipping beyond the horizon off the Namibian coast, however, she was never seen again.
Her last communication with her owners was on September 6. After that, silence.
Then, two weeks ago, the Satsang was spotted by a bulk carrier, the Poseidon.
She was drifting alone in the ocean currents about 220 miles south of Port Elizabeth, her tow wire hanging straight down, and of the Jupiter 6 there was no sign.
But the mystery of how the tug met its fate has only deepened.
Could she have been afloat until recently, her crew battling to the last to keep her from sinking, with no working radios with which to call for help, or did she sink weeks ago?
If she had sunk some time ago, the signal from the beacon would not have been heard now, the rescue centre spokesman said.
"These beacons have a battery life of only 90 hours. Even if it went down with the ship and only popped up now, its battery would have been activated already.
"We would not have heard the signal because it would have been under water and the battery would have been dead by the time it surfaced," he said.
But if the tug had been struggling to stay afloat, why did the crew not take to their liferafts?
The Satsang was finally taken in tow by the South African salvage tug Smit Amandla last week after waiting for days to get salvors aboard the derelict in rough weather.
Salvors who boarded the Satsang reported that the tow rope attached to her bow had been snapped and that two emergency towing rigs assumed to have been set up by the Jupiter 6 crew had also failed.
Such evidence indicated that the Jupiter 6's crew had a terrible battle to try to reconnect their tow twice during bad weather.
"Who knows what could have happened? There can be so many theories," said David Main of Smit Marine South Africa.