Most sea turtle species live in warm water. You don't find abundantly numbers in the North Sea. However every once in awhile, a weakened animal is carried by the currents. Sometimes the Gulf Stream leads it into the North Sea. Green turtles in particular are the most common turtle species to wash ashore along the North Sea coast. These turtles are shipped across the world for human consumption. Leatherbacks live where jellyfish, the major part of their diet, are plentiful. That's why they occasionally swim in colder seas, such as the North Sea.