I watched an old episode of the BBC series Coast last night and it featured a Leatherback Turtle that had washed ashore near Harlech
It was 9 feet long nose to tail and 9feet from flipper to flipper weighing in at around 100ST!
The startling thing is that they are not lost,but actually live around Britain and Ireland eating jelly-fish these 6foot reptiles do an annual migration from
around the Cape verde islands.
http://www.turtle.ie/ is a site tracking an Irish tagged Leatherback