Jökulsárlón is a large glacial lake in southeast Iceland, on the borders of Vatnajökull National Park. Situated at the head of Breiðamerkurjökull, it developed into a lake after the glacier started receding from the edge of the Atlantic Ocean (as per Wiki).
Floating around these huge old chunks of ice, some of which have been tainted with ash, is quite a surreal experience and a photographers dream!