 HMS Amphion was an Active @-@ class scout cruiser built for the Royal Navy before the First World War . Completed in 1913 , she was initially assigned to the First Fleet and became a destroyer flotilla leader in mid @-@ 1914 . When the war began , her flotilla was assigned to the Harwich Force . While patrolling on the first full day of the war , Amphion and her destroyers encountered and sank a German minelayer , SMS Königin Luise , but not before she had laid many of her mines . While returning from patrolling the following morning , Amphion accidentally struck a mine on 6 August 1914 off the Thames Estuary and sank with the loss of 132 crewmen killed . She was the first ship of the Royal Navy to be sunk in the First World War . The wreck site is protected and may not be dived upon without permission from the Ministry of Defence . 
