sentences:  "Undine" was transferred back to the Detached Division on 13 April 1915 to take part in an operation the next day to bombard Russian positions at Memel and Buddendiekshof; the attacks continued through 17 April, after which "Undine" returned to the Coastal Defense Division.On 7 November 1915, "Undine" was steaming north of Arkona with a pair of torpedo boats as escort for the ferry "Preussen" as it moved from Trelleborg to Sassnitz.She was attacked by the British submarine , under the command of Lieutenant Commander Francis Cromie.