The Child from the Sea
One day in the olden times, a fisherman from Errismore was fishing for gurnet. The day was very fine, and fish were plentiful. Toward evening, the fisherman felt a great weight on his line and thought that he had hooked a heavy fish. He started to haul it in, and when he had it on board, what had he caught but a male child! His hair was as red as the coat of a fox. The hook was stuck into his cheek. The fisherman was very proud of his catch. The boy ran up under the forward thaft of the boat and stayed there.
The fisherman took him home, but as soon as he let him down on the floor the boy rushed in under a bed, and even a man with a pitchfork couldn't get him out. There he stayed until the following day. They tried by every means to get him to eat and drink, but it was no use. The man went to the priest and told him what had happened.
"You must take him out again, as close as you can to the spot where you caught him," said the priest, "and put him back into the sea again."
The fisherman took him in the boat next day and rowed toward the place where he had caught him. When they were near the spot, the boy gave a big laugh. He jumped, legs up, out of the boat, dived down like a cormorant, and was seen no more.
Apparently, stories of a hidden world under the sea, populated by humans, were pretty common in the past. This one, told by Val O Donnchadha in 1939, doesn't have any seals in it, but it wouldn't have been unusual if it did. A thaft is a fisherman's seat in a boat. A gurnet is a type of fish (also spelled gurnard) that lives along the bottom of the sea. It's known for grunting when caught.