She was equipped with German-built MAN Diesel engines and spent her career in World War II in western European waters, in the North Sea and off the west coast of France, and most famously taking part in Operation Frankton.

An attack also failed on the German tanker Benno, formerly the Norwegian Ole Jacob, which had also been captured earlier by the Atlantis.

[5] In January 1941 Tuna and the submarine Snapper were escorted by the captured French minesweeper La Capricieuse as far as Bishop Rock, Isles of Scilly.

[6][self-published source][7] Later that month Tuna engaged and pursued an unidentified surfaced U-boat at night for more than an hour.

[8] In February 1942 the boat was ordered towards the Trondheim area along with HMS Trident to protect a convoy from enemy sorties from Norwegian ports.

[9][self-published source] On 30 November 1942, under the command of Lieutenant-Commander Dick Raikes DSO, Tuna sailed from Holy Loch, Scotland, inserting twelve Royal Marines swimmer canoeist commandos soon to become the SBS into the Gironde estuary as part of Operation Frankton (the attack on Bordeaux harbour).

[13] For his superb navigation and coolness under pressure, Lieutenant-Commander Dick Raikes was awarded the Distinguished Service Order,[14] and was later played by Christoper Lee in the 1955 film The Cockleshell Heroes.

For the destruction of three U-boats during those patrols, her commanding officer, Lieutenant D. S. R. Martin, was awarded the Distinguished Service Order with two bars.