The objects projecting up from the sand are tree stumps, remnants of an ancient forest of about 5000 years of age. Legend has it that the forest was on land that extended out into Cardigan Bay for about 20 miles from here but the land became submerged by the sea. The submerged land is known as Cantre'r Gwaelod and, like many parts of Wales, it is the subject of much myth and legend .

http://www.bbc.co.uk/legacies/myths_legends/wales/w_mid/article_1.shtml