The boat house is a single storey rubble building on the rocky eastern side of the peninsula at the southeast end of the breakwater, facing north into Pilot's Cove. The building measures 5m north to south by approximately 13.5 m overall and there is a red-brick arch to the full-width opening at the northeast end; the eaves of the building are level with the ground on the landward side. A new roof was erected in 1992.
Site visited B.A.Malaws, RCAHMW, 14 January 1992.

Event and Historical Information:
A light was established on Llanddwyn in 1823 by Caernarfon by Caernarfon Harbour Trustees as a navigational aid for entering the Menai Straits and Caernarfon Harbour. The community here supported pilots and pilot boats. The cottages on Llanddwyn island are now used as craft workshops.

Sources:
Hague, D, 1994, Lighthouses of Wales: Their Architecture and Archaeology, pg58-60
Lloyd, L, 1989, The Port of Caernarfon, 1793-1900, chapter 9.

Maritime Officer, RCAHMW, December 2008.