Sully Island

It is located 400 m (440 yd) off the northern coast of the Bristol Channel, midway between the towns of Penarth and Barry and 10 km (6 mi) south of the Welsh capital city of Cardiff.

Cargo arrived and departed via the St Mary's Well Bay Road, which is now blocked off to through traffic, en route for the traditional market at Canton Cross in Cardiff.

During the 16th century several historical records show that the trader masters were supposed to pay an import duty to local officials, but many attempted to avoid the payments by smuggling the cargoes ashore.

In 1569 court records show that the harbour official seized contraband consisting of 28,000 lb (13,000 kg) of cheese and eighty barrels of butter arriving illegally at Swanbridge.

A small fleet of fishing vessels were located at Swanbridge harbour and it is likely that the row of cottages, that were converted during 1976 and 1977 into the Captain's Wife pub, were the traditional homes of the local fishermen and their families.

The survey ship that the oceanographer William Speirs Bruce used on the Scottish National Antarctic Expedition, 1902–04, was originally a sealer named Hekla, built in Norway in 1872.

From 1890 until the end of the 1960s, Swanbridge was connected northward to Penarth and Cardiff and westward to Barry and the South Wales Valleys by an extension of the Taff Vale Railway line.

The redundant rail track bed has mostly been sold into private ownership and built on, with any unsold stretches being overgrown and impassable as far as the Fort Road bridge at Lavernock.

When the rail link arrived at the start of the 20th century, the bays of Swanbridge, St Mary's Well and Lavernock became popular summer time destination for day trippers from Cardiff, Penarth and the South Wales Valleys, particularly at weekends and on bank holidays.

For nearly a hundred years there was a busy and profitable cafe and ice cream parlour, located at the St Mary's Well Bay end of the Swanbridge carpark, that was closed and demolished around 1970 when the through road was blocked off to traffic.

The sea cliff exposures of Sully Island provide an excellent insight into the environment of the area in Triassic times, approximately 200 million years ago.

Red mudstones, sandstones and breccias (rocks made from angular pebbles) indicate that this area was a beach situated on the margin between steep semi-desert land and a large shallow lake or marine lagoon.