The giant leatherback turtle released back into the sea over a week ago in Co Kerry is giving back signals from her electronic tag and is now over 330km (205 miles) south-southwest of Dingle, heading for the mid-Atlantic.
She has been averaging around 45 km a day but is now facing her greatest danger on her way to the Caribbean Sea, according to marine officer and rare fish expert Kevin Flannery.
The Japanese long-line tuna vessels with hundreds of miles of hooks set with squid will be "her main obstacle", Mr Flannery said. "We hope she finds her way through. We shall see."
Local fisherman Pádraig Sullivan found the turtle caught on the buoy ropes of his lobster pots in Dingle Bay and alerted Mr Flannery.
The 70-stone turtle was found to be female and 100-years-old. She recovered in Dingle Ocean World, where she was tagged.
The Dingle leatherback is the first to be tagged in European waters as part of a joint project between the University of Wales at Swansea and University College Cork.
It only appears in Irish waters during the summer and early autumn.
She has dived to depths of over 60m (197ft) in the past days and was at 330km south-southwest at 10am yesterday.
It is not certain she is on her way to the Caribbean waters and beaches where she will lay her eggs. She could be equally on her way to Africa, Mr Flannery said.
The whole point of the Irish Sea Leatherback Turtle project, as it is known, is to solve the mystery of the leatherback's journeys, he added.
Her movements are being tracked on the project's website at www.turtle.ie