St. Catherines Island, Ynys Catrin in Welsh, is a tidal island that is accessible at low tide. The island has a fort that is open to the public. Caldey, Ynys Bŷr in Welsh is the home of a group of Cistercian Monks that live at the monastery situated on the island. The name Caldey is derived from the old Viking name for the island Kald ey meaning Cold Island, whereas the Welsh name refers to a 6th century Abbot called Saint Pyr.
Caldey Island in fact consists of two islands that are joined at low tide. The second island is known as St. Margaret’s island and is the home of many seals and birds. Caldey is also famous for its flowers, many of which are not common in other parts of Britain. There are ferries to Caldey Island every half an hour during the spring and summer from Tenby harbour.