 Hubbard stated in his eighteen @-@ page after @-@ action report that he had intended to force the submarine to surface so that it could be attacked by the surface vessels ' guns . He reported that his vessel had seen oil on the surface , though the PC @-@ 815 took no samples , and asserted that the blimps had seen air bubbles , oil and a periscope , though the blimps ' own reports did not corroborate this . No wreckage was seen , despite the heavy depth @-@ charging . The PC @-@ 815 sustained some minor damage and three crew were injured during the incident when the ship 's radio antenna was accidentally hit by gunfire . At midnight on 21 May , with depth charges exhausted and the presence of a submarine still unconfirmed by any other ship , PC @-@ 815 was ordered back to Astoria . 
