Isle of Man Steam Packet Company England, Wales, Scotland and Ireland. Ports served included Liverpool, Silloth, Whitehaven, Holyhead, Ardrossan, Blackpool, Belfast and Dublin. Vessels and crews of the company were actively involved in both the First and Second World Wars. One vessel, , was attached to the British Grand Fleet and led the German High Seas Fleet into Scapa Flow in the Orkney Islands at the end of the First World War. Another vessel, "Viking", was converted to become a seaplane carrier, serving as . During the First World War, eleven out of a total fleet of fifteen Steam Packet ships were requisitioned by the Admiralty.
Romanian Black Sea Fleet during World War I sea-going gunboat "Grivița" and the Romanian Navy's sole proper minelayer, "Alexandru cel Bun". The Black Sea Fleet was neglected for a long-time by the Romanian Command. Its warships were all built between 1880 and 1888, while the Romanian Danube Flotilla was equipped with modern vessels built as late as 1908. The protected cruiser "Elsiabeta" was converted to an anti-aircraft cruiser after the start of the war, her four 120 mm main guns being landed and her four 75 mm secondary guns being modified for anti-aircraft fire. She was also armed with four machine guns and four 356 mm (12 inch)