Sully Island Walk
This walk takes you to Sully Island in the Vale of Glamorgan.
You can reach the island at low tide from the hamlet of Swanbridge. Located 400 metres from the mainland, the island is accessible on foot at low tide from the car park of the Captain’s Wife pub via a rocky causeway. The crossing is only safe for approximately three hours on either side of low tide, after which the island is cut off until the next cycle. A tide table is displayed at the crossing point to indicate when it is safe to walk across. You can also see the tide times for the island by clicking here.
Sully Island has a rich history dating back to ancient times, with evidence of visits by Romans and Vikings. The island also contains the remains of a Saxon promontory fort and a Bronze Age burial mound at its highest point. In the Middle Ages, the island was associated with smuggling and piracy, notably serving as a base for the Norman pirate Alfredo de Marisco.
The walk offers scenic coastal views of the Bristol Channel and the surrounding cliffs, with glimpses of Penarth, Barry, and Cardiff in the distance. The island itself is covered in coarse grass with few trees or shrubs due to the exposure to sea winds. A damp central depression supports a small reed bed, providing a unique habitat for wildlife. The island was once home to a thriving rabbit colony, though numbers declined after the spread of myxomatosis in the 1950s. Occasionally, new colonies establish themselves, but never to the extent seen in earlier times.
To continue your walking in the area head to the nearby Cosmeston Lakes Country Park where you can enjoy some pleasant waterside trails. The wildlife rich Flat Holm island can also be reached from nearby Cardiff.
Sully Island Ordnance Survey Map 
- view and print off detailed OS map
Sully Island Open Street Map 
- view and print off detailed map
Sully Island OS Map 
- Mobile GPS OS Map with Location tracking
Sully Island Open Street Map 
- Mobile GPS Map with Location tracking
Cycle Routes and Walking Routes Nearby
Photos
Sully Island. The waters around Sully Island are a popular fishing spot, with species such as cod, bass, dogfish, and conger eel found in the area. Botanists have recorded unusual plant species, including bee orchids, marine spleenwort, and adder’s tongue fern. The sea cliffs on the island expose Triassic rock formations, offering insight into the region’s geological history, with layers of red mudstone, sandstone, and breccias revealing an ancient coastal environment that existed over 200 million years ago.
This walk provides an opportunity to explore both the natural beauty and the historical significance of Sully Island. However, caution is necessary when crossing due to the rapid return of the tide, which has led to many walkers becoming stranded over the years.
View north along the causeway from Sully Island
Sully Island
Swanbridge foreshore