A massive rock, with the form of a jagged tooth, Am Plastair is located off the north coast of Soay in the remote St. Kilda group of islands, 56 miles (90 km) west of South Harris. It reaches a height of 45m (147 feet), with an area of only 0.58 ha (1.4 acres). A 40-m (131-feet) long underwater tunnel runs through the rock, narrowing and rising from 24m (78 feet) below sea level on the north side to just 4m (13 feet) deep to the south. This provides a dangerous challenge for divers.
