The device measures ultra-violet levels and tells bathers how long it is safe to stay out. It was built by the school's engineering club, which has already ploughed the Pounds 1,000 winnings into next year's project.
Other winners were: Distinguished commendation (plaque plus Pounds 500): Churchdown School, Gloucestershire, Teignmouth Community College, Devon, Turves Green Girls' School, Birmingham.
Highly commended (plaque): Carisbrooke High School, Isle of Wight, Chipping Norton School, Oxon, Maltravers School, Wiltshire, Sidmouth College, Devon, and Tavistock College, Devon.
Other finalists (certificate): Collington School and Community College, Cornwall, Carr Hill High School, Preston, Hall Garth School and Kings Manor School, bothin Cleveland, Lytchett Minster School, Dorset, Queensbury School, Bradford, Sunbury Manor School, Surrey, and Worthing High School, West Sussex.