 The first recorded action of U @-@ 70 under the new rules of engagement occurred near the end of February 1917 , when the U @-@ boat shelled the British @-@ flagged SS San Patricio . The 9 @,@ 712 GRT tanker , encountered by U @-@ 70 off the Orkney Islands , survived the attack . In March , U @-@ 70 sank twelve ships totaling 25 @,@ 708 tons and damaged a thirteenth of 4 @,@ 666 tons . 
