Strange things can happen at sea, as the crew of Liberian-flagged oil tanker Willowy confronted a mysterious incident on Sunday.
In the early hours of Sunday 31 May, senior officers aboard the oil tanker Willowy were called to the bridge to be told that their ship and four others in its vicinity were mysteriously sailing in circles, unable to steer, and on course to converge.....MORE
It must be easy to panic at sea. The immediate presumption was that strong currents were pushing the vessels around, but there were no such currents where the ships were sailing in the south Atlantic Ocean, west of the South African city of Cape Town.
Ships appearing to sail in circles have become an increasingly common and mysterious phenomenon near a number of ports on the coast of China, especially near oil terminals and government facilities - but nothing had been seen where the Willowy was.
Researchers monitoring these bizarre circles near the Chinese coast believe they are probably the result of systematic GPS manipulation designed to undermine a tracking system which all commercial ships are required to use under international law.
Known as AIS (automated identification system), the technology broadcasts unique identifiers from each vessel - along with the vessel's GPS location, course and speed - to other ships nearby.
These signals are even collected by satellites and used to monitor suspicious behaviour, including smuggling, illegal fishing, and - most relevantly - trade in sanctioned oil.
The circles spotted near the Chinese coast have been attributed to GPS interference, something which coincided with US sanctions on Iran, according to Phil Diacon, the chief executive of marine intelligence firm Dryad Global.
But according to a global analysis of this data by environmental groups SkyTruth and Global Fishing Watch, a number of circling incidents have also occurred quite a distance away from Chinese ports, with some impossibly appearing miles inland near San Francisco....
