”M/S Söderarm” is a passenger ship built in 2003 at Riga Shipyard, Latvia and fully equipped in 2004 at Moen Slip A/S, Norway to be delivered to Waxholms Ångfartygs AB, Sweden. After a christening on 22nd of April 2004, “Söderarm” was put in service in the Stockholm's archipelago. Later in September 2004, the ship’s lifeboats were re-positioned at Oskarshamn’s shipyard not to obstruct the back mirrors. On 17th of April 2009 the vessel was recertified for 500 passengers, up from the previous capacity of 350. On 18th of April 2016, the operation of the ship was transferred to TRSM Group 1 AB, Stockholm. New engines, Mitsubishi S6R2, 1.755 hp (1,290 kW), were installed the same year. On 20th of April 2017, the operation of “Söderarm” was taken by Rederi AB Faludden, Stockholm, however since 1st of October 2019 the management and operation of the ship is administered by Blidösundsbolaget AB, Stockholm.