March 6, 2014 — The satellite-tagged 4.4m-long female is currently swimming above the mid-Atlantic ridge – which marks a rough boundary line between east and west.
Lydia was first tagged off Florida as part of the Ocearch scientific project.
The shark has travelled more than 30,500km (19,000 miles) since the tracking device was attached.
"We have no idea how far she will go, but Europe, the Med, and the coast of Africa are all feasible”Dr Gregory Skomal, senior fisheries biologist with Massachusetts Marine Fisheries, told BBC News: "No white sharks have crossed from west to east or east to west."
Lydia is now roughly 1,600km (1,000 miles) from the coasts of County Cork in Ireland and Cornwall in Britain, and nearly 4,800km (3,000 miles) from Jacksonville, Florida, where she was tagged by scientists in March 2013.
Dr Skomal explained: "Although Lydia is closer to Europe than North America, she technically does not cross the Atlantic until she crosses the mid-Atlantic ridge, which she has yet to do.