The isle of Jethou is around three-quarters of a mile to the southwest beyond Point Sauzebourge. It is possible that in AD 709 a storm washed away the strip of land that connected Jethou to Herm. About off the northern coast of Jethou is the islet of Crevichon, which measures about by , with an area of less than three hectares. To the west, between Herm and Guernsey, lies the channel Little Roussel (Petit Ruau); between Herm and Sark, to the east, lies the Big Roussel (Grand Ruau). Bréhon Tower, a Victorian-era fortification, is in the Little Roussel between Herm and Saint Peter Port. The tower was created between 1854 and 1856 by Thomas Charles de Putron (1806–1869) using granite from Herm.