Abercastle is a small harbour / beach on Pembrokeshire's north coast. A small (free) parking area overlooks the beach and access to the shore is down a short slipway. Facilities here include (seasonal) toilets and a picnic table. The village of Trefin is a short walk away, and has a cafe and a pub.
The beach is mostly seaweed strewn sand, with the tidal island of Ynys y Castell on the eastern side.
It's very sheltered and is popular with anglers, canoeists and divers. The fragmented wreck of the Leysian - a steamship which hit rocks in February 1917 on its way to Barry - is situated just outside the bay at about 15 metres depth.