During the war with Russia, Otter in HMS "Alban" took part in the surveys carried out in the Baltic, under the command of Bartholomew Sulivan, in support of fleet operations. The most successful action was the capture and destruction of the fort at Bomarsund, located where the Gulf of Finland and the Gulf of Bothnia join the Baltic, in August 1854. The surveys of the channels between the various islands of Åland were crucial in enabling the transport of the French and British troops to their landing places. He was promoted to captain in September 1854. The following year, Otter was in command of HMS "Firefly". On 9th June, while surveying near the fortress of Kronstadt, the "Firefly" and were struck by mines ("infernal machines"). Both ships were damaged, but neither was put out of action. This was one of the first successful uses of mines in naval warfare. In early August, "Firefly" bombarded Brandon, the port and shipbuilding centre near Vasa, destroying the magazines and also capturing several vessels and stores.