Harold Boase was born on 18 March 1892, the son of Edward and M E Boase of Penzance, Cornwall. He joined the Royal Navy as a Cadet in January 1905. After time in HMS DRAKE, he joined submarines in February 1914 and, as a Sub Lieutenant, was appointed to HMS C29 as First Lieutenant in June 1914.

Promoted to Lieutenant in December 1914, Boase was appointed to HMS D8 as First Lieutenant in October 1915 and as First Lieutenant of E45 in July 1916. His first Command appointment was to HMS C16 in December 1916.

On 16 April 1917, C16 was dived at periscope depth, when she was in collision with the Destroyer HMS MELAMPUS. The submarine was damaged and hit the bottom at 60 feet. It appears that all the crew survived the collision and the bottoming but all attempts at escape failed and the whole crew was lost.

Harold Boase is buried at the Shotley (St Marys) Churchyard, Suffolk in the Submarine Enclosure.