At 15.30 hours on 13 Sep 1939, U-29 tried to stop the unescorted Neptunia (Master Joseph Cordery) about 270 miles west-southwest of Cape Clear by a shot across her bow, but the tug did not stop and used its radio. She was en route to assist HMS Walker (D 27) (Cdr W.J.C. Robertson, RN), which had been badly damaged in a collision with HMS Vanquisher (D 54) (LtCdr K.H. Fraser, RN) while escorting convoy OB-2 southwest of Ireland on 11 September. After the first hits, the crew immediately abandoned ship in a motor boat. The Germans questioned the master and then sent the boat with a boarding party to the ship. However, the U-boat recalled the men shortly after they went aboard in order to sink the vessel quickly by a torpedo, but was forced to sink the tug by gunfire after firing two torpedoes that detonated prematurely. On 15 September, the survivors were picked up by the Brinkburn.