There has been a history of sea monsters in some areas of Wales; in particular the Menai Straits Barmouth area and further up the coast in North Wales.
In 1805 in the Menai Straits, A ship reported it had been attacked by a sea serpent, which wrapped itself around the ships mast until the crew attacked it and it fell into the sea. They claimed it followed the vessel for two more days before giving up.
In 1882 another sighting according to this letter from Nature Magazine:
About three P.M. on Sunday, September 3, 1882, a party of gentlemen and ladies were standing at the northern extremity of Llandudno pier, looking towards the open sea, when an unusual object was observed in the water near to the Little Orme's Head, travelling rapidly westwards towards the Great Orme. It appeared to be just outside the mouth of the bay, and would therefore be about a mile distant from the observers. It was watched for about two minutes, and in that interval it traversed about half the width of the bay, and then suddenly disappeared. The bay is two miles wide, and therefore the object, whatever it was, must have travelled at the rate of thirty miles an hour. It is estimated to have been fully as long as a large steamer, say two hundred feet; the rapidity of its motion was particularly remarked as being greater than that of any ordinary vessel. The colour appeared to be black, and the motion either corkscrew-like or snake-like, with vertical undulations. Three of the observers have since made sketches from memory, quite independently, of the impression left on their minds, and on comparing these sketches, which slightly varied, they have agreed to sanction the accompanying outline as representing as nearly as possible the object which they saw. The party consisted of W. Barfoot, J.P., of Leicester, F. J. Marlow, solicitor, of Manchester, Mrs. Marlow, and several others. They discard the theories of birds or porpoises as not accounting for this particular phenomenon.
F. T. MOTT.
Birstall Hill, Leicester, January 16th, 1883.
The Mawddach Estuary at Barmouth has been the place of a few sightings in the last 100 years. In “Mysterious Wales” by Chris Barber (Blorenge Books June 1999) a local woman claimed to have found four large footprints in the sand, described as being ‘as big as an elephant’s’. In 1937 a crocodile like animal was witnessed by a Harlech man as it walked along the river bank
Then in March 1975 six schoolgirls described a creature they encountered on Barmouth beach. ‘It had a long neck and a square face and a long tail with a flipper at the back and its skin was black and patchy’.. `It was like a dinosaur,'' said one of the girls. `The monster was about 10 feet long, with a long tail, long neck and huge green eyes. It walked towards the sea and entered the water.'' Its green eyes peered at them before sinking beneath the waves. The girls fled in terror.
(N.B. Sounds like the classic long necked pinniped description to me, but could just have been an ordinary large member of the seal family. They can appear to have long necks if they stretch it out).
It is not the only strangeness in that area though:
In September 1922 John Morris and William James saw an object fall into the ocean off Barmouth shore , so slowly that it was thought to be a plane. A boat was sent out, but nothing was found. (Magonia #45, Fort 639)
It is odd how places that report one phenomenon, such as sea serpents, also seem to have others occurring. Does the area attract strange things or does it just attract the sort of people who see strange things….one to ponder over.