Sevenstones Lightship

Sevenstones Lightship is a lightvessel station off the Seven Stones Reef which is nearly 15 miles (24 km) to the west-north-west (WNW) of Land's End, Cornwall, and 7 miles (11 km) east-north-east (ENE) of the Isles of Scilly. The reef has been a navigational hazard to shipping for centuries with seventy-one named wrecks and an estimated two hundred shipwrecks overall, the most infamous being the oil tanker Torrey Canyon on 18 March 1967. The rocks are only exposed at half tide. Since it was not feasible to build a lighthouse, a lightvessel was provided by Trinity House. The first was moored near the reef on 20 August 1841 and exhibited its first light on 1 September 1841. She is permanently anchored in 40 fathoms (73 m) and is 2.5 miles (4.0 km) north-east (NE) of the reef. Since 1987, the Sevenstones Lightship has been automated and unmanned.

The Seven Stones lightvessel also acts as an automatic weather station. A series of Trinity House lightships stationed near the Sevenstones Reef have measured significant wave heights (Hs or SWH)—the periodic average of the highest one third of waves in a spectrum—since the early 1960s using Ship Borne Wave Recorders (SBWR). The Sevenstones Lightship is in a very exposed location and is open to most North Atlantic storms.