Her first real duty was escorting the Arctic convoy PQ-18 to the Russian port at Murmansk. On 20 September, she was required to assist the destroyer which had been torpedoed by the German U-boat . Although the stricken ship was already being assisted by , and although destroyers , and the naval trawler were also on hand to assist the ship, the gales and rough seas proved too much for her and she sank on 24 September. "Opportune" helped transport some of "Somali"s survivors to Scapa Flow.