Another reported problem with the Type UB Is was the tendency to break trim after the firing of torpedoes . The boats were equipped with compensating tanks designed to flood and offset the loss of the C / 06 torpedo 's 1 @,@ 700 @-@ pound ( 770 kg ) weight , but this system did not always function properly ; as a result , when firing from periscope depth the boat could broach after firing or , if too much weight was taken on , plunge to the depths . When UB @-@ 15 torpedoed and sank Italian submarine Medusa in June 1915 , the tank failed to properly compensate , forcing the entire crew to run to the stern to offset the trim imbalance .