 UB @-@ 50 's fourth patrol was very successful . In less than a month , she sank six vessels . The first victim was the 2 @,@ 457 GRT French steamer Saint Jean Ii , which went down 22 March 1918 off of Cap Bon . That same day , UB @-@ 50 managed to damage the British steamer Shadwell off of Bizerta . Four days later UB @-@ 50 sank the 11 @,@ 495 GRT Italian steamer Volturno off of Bone ( Annaba ) , Algeria . On 6 April , UB @-@ 50 sank the French vessel Madeleine Iii and on 11 April , she sank the Italian sailing ship Carmela G and the British vessel Highland Prince . 
