Daniel Halloran was born in Devonport, Devon, on 11 May 1909, the son of Petty Officer Patrick and Catherine Halloran. He joined the Royal Navy directly from school as a Boy Artificer at HMS FISGARD on 31 December 1924. On completion of his Engine Room Artificer Apprenticeship, he was drafted to the battleship HMS RENOWN and served in that ship until 21 September 1932, when he was drafted to the cruiser HMS BERWICK. He next served in the battleship HMS QUEEN ELIZABETH for a year before transferring to the battleship HMS BARHAM from 24 October 1933 to 11 January 1935.

Daniel Halloran joined submarines at HMS DOLPHIN on 24 January 1935, serving in HMS L54 from 11 May 1935 to 20 January 1936 and then in HMS OBERON until 21 October 1936. This was followed by a draft on 22 October 1936 to HMS GRAMPUS. He was promoted to Warrant Engineer on 1 July 1937 and, following Officers courses and a period in General Service, he returned to HMS DOLPHIN on 24 April 1939.

An appointment to the Submarine Depot Ship HMS TITANIA followed on 16 August 1939. On 22 November 1939, he was appointed to the Submarine Depot Ship HMS CYCLOPS, and to HMS SNAPPER as Engineering Officer on 27 April 1940. He was Mentioned in Despatches, see the London Gazette dated 6 September 1940.

SNAPPER left for her thirteenth war patrol on 29 January 1941. Three German minesweepers are reported to have conducted depth charge attacks on a submarine on 11 February 1941 – after the minesweepers had been attacked. SNAPPER failed to return from her patrol and is presumed to have been sunk near Ushant on 11 February 1941.

Daniel Halloran is commemorated on the Portsmouth Naval Memorial on Panel 46 Column 1.