Sonar searches by an Estonian minesweeper, Ugandi, have found the remains of 3 British ships that were part of a squadron that was supporting the Baltic states’ struggle for independence against both German and Soviet invaders in 1918 / 1919.
The cruiser HMS Cassandra was sunk by an uncharted German mine on 5th December 1918 with the loss of 11 of her crew of 400. Two Flower Class sloops, HMS Myrtle and HMS Gentian, were sunk by mines in July 1919 while clearing a passage to try and supply the independent Estonian government with weapons. Nine men were lost.
The ships apparently lie in around 60-100 metres of water near the island of Saaremaa.
There is more information on the Guardian’s website.