Passage below comes from the book "Irish Folk & Fairy Tales Omnibus" by Michael Scott
Chapter 10
The Uncovered Land
"Shea watched the tide slowly receding down Dingle Bay, uncovering the soft wet ground beneath to the early morning sunlight. He stood in the saddle until the waters passed the low watermark and beyond. It had been seven years since he had last witnessed this event - seven years since he had first heard the legend of the Uncovered Land.
"Legend had it that the bay had once been part of the land, a broad plain stretching from what was now the Great Blasket Island to Valencia in the south. But when the remnants of the Tuatha De Danann had returned to the land, their magicians had caused the Great Western Ocean to roll across the green and fertile land, whilst they remained safe in their enchanted kingdom of Tir fo Thuinn, the Land Beneath the Waves.
"However, every seven years the sea receded almost to the horizon and exposed the elven land to the light of the life-giving sun. And then the descendants of the People of the Goddess would come forth and sing and dance for a short while on the dry land until the tide turned and the magical land was covered for another seven years."