Tonn Clidna
Prose Dindsenchas

Clidna daughter of Genann son of Tren went out of Tulach Da Roth ("Hill of Two Wheels"), out of the Pleasant Plain of the Land of Promise, with Iuchna Curly-locks to get to the Mac Oc. Iuchna practised guile upon her. He played music to her in the boat of bronze wherein she lay, so that she slept thereat, and then he turned her course back, so that she rounded Ireland southwards till she came to Clidna.

This is the time at which the illimitable seaburst arose and spread throughout the regions of the present world. Because there were at that season Erin's three great floods, namely, Clidna's flood and Ladru's and Baile's; but not in the same hour did they arise: Ladru's flood was the middle one. The flood pressed on aloft and divided throughout the land of Erin till it caught the boat and the damsel asleep in it on the beach. So there she was drowned, Clidna the Shapely, Genann's daughter, from whom "Tonn Clidna" ("Clidna's Wave") is named.

SOURCE

Ancient Irish Tales. ed. and trans. by Tom P. Cross & Clark Harris Slover. NY: Henry Holt & Co., 1936