Llyn Glaslyn in Wales is 126 feet (42 metres) deep and is said to be the location of a legendary monster the 'Afanc.'
The Afanc was a mythical water monster that originally abided in Llyn-yr-Afanc (the Afanc Pool) in the River Conwy. It was a huge beast who would cause flooding to the local area by its thrashing about. Attempts had been made to kill it but to no avail. It was decided to try and entice the creature from the pool and move it to a place where it could not cause any more trouble. Iron chains would be used to bind the creature and two oxen would then drag the creature to another lake. A local girl sang by the lake and the creature left the lake to get closer to her. Local men immediately bound the creature and started to drag it to Llyn Ffynnon Las (now called Llyn Glaslyn). The creature apparently jumped into the new home on arrival and is said to be trapped there.