Gilbert Welman was born in St. Columb, Cornwall on 16 September 1888, the son of Henry Acton Welman and Mary Letitia Welman of Trewarthenick. Grampound Road, Cornwall. He joined the Royal Navy as a Midshipman in February 1905 and served in HMS JUPITER and HMS INVINCIBLE.

He joined submarines as a Sub Lieutenant in January 1910. Promoted Lieutenant in December 1910, his first recorded submarine appointment was to HMS C36 in Hong Kong in April 1911. On his return from Hong Kong, he was appointed to HMS ONYX, the Depot Ship of the First Submarine Flotilla at Devonport, and then to command HMS A7 in November 1913.

A7 was lost with all hands in an accident in Whitsands Bay off Cornwall on 16 January 1914. The submarine was not recovered.