A stone well-head building, a unique feature serving a lighthouse in Wales, presumed by Hague (1991, 52) to date from the early William Tench period after 1716. The stone building is D-shaped with an apsidal end, comprising a door on the north side, and an inclined roof made of three trimmed stone slabs. Inside the well-house steps lead down into the water, well over 1m in depth. Hague suggests the well may also have played a role in baptisms on the island.

Visited by T. Driver, RCAHMW, 19 April 2016.