Sully Island is a small tidal island a kilometre off the coast of south Wales, between Penarth and Barry.
Its name may mean "south lea" or "south pasture" or, like the nearby village of Sully it may be a family name. The rate of tidal rise and fall in the area is the second highest in the world: only that of Bay of Fundy, Nova Scotia is greater. A causeway connecting the island to the mainland is uncovered for approximately 3 hours either side of low tide; the island is cut off from the mainland for the rest of the day. This makes Sully Island a dangerous place and many people have been swept to their deaths while trying to leave the island as the tide rises.
The British biologist Brian J. Ford used to write at Swanbridge and explored Sully island. He also carried out ecological studies, and mapped the island and foreshore. Ford recorded many plants unusual for the area, including the bee orchid, the marine spleenwort and the adder's tongue fern.
Other facts -
- A mile west of the island, but on the mainland at The Barracks, is Bendricks Rock that has the only known Upper Triassic dinosaur – Tetrasauropus – footprint site in Britain
- A Saxon fort lies on the island's south-eastern headland. Some people believe that this was a Saxon stronghold, while others believe it was a defended homestead rather than a full settlement
- The waters around Sully Island are fished for species such as cod, whiting, pouting, dogfish and bass
- During the 13th century, the island was the base for "De Marisco", a Norman pirate known as "The night hawk". In later years, it was known for its involvement in the local smuggling trade.