More and more leatherbacks are being spotted around the coast of Britain and Ireland, suggesting the turtles are trawling our waters for their favourite food - jellyfish.
Following the Welsh discovery, marine ecologists at Swansea University and University College Cork used satellite-tracking systems to follow 10 leatherbacks from their nesting sites in the tropics.
Pollution also poses a threat: floating plastic bags look a lot like the jellyfish they rely on as their main food source, and have been found in the digestive systems of about half of the leatherbacks studied in recent times.
Each time the leatherbacks surface to breathe, the transmitters attached to their shells send data about their location, water temperature and water depth via satellite, allowing marine biologists to track their progress with GPS precision.