SM UB-18 - Mined December 1917 SM UB-19 - Sunk by Q-ship Penshurst November 1916 SM UB-20 - Sunk by aircraft July 1917 SM UB-21 - Foundered on way to breakers 1920 SM UB-22 - Mined January 1918 SM UB-23 - Broken up 1921 SM UB-24 - Broken up 1921 SM UB-25 - Broken up 1922 SM UB-26 - Sunk and raised by French Navy repaired as Roland Morillot BU 1931 SM UB-27 - Sunk by HMS Halcyon July 1917 SM UB-28 - Broken up 1919 SM UB-29 - Previously thought being sunk by HMS Landrail, but possibly mined December 1916 (wreck discovered in 2017, which contradicts the credit to HMS Landrail.