 The incident attracted the attention of the naval high command , as there had been a verified Japanese submarine attack against Fort Stevens about 50 miles further north in June 1942 and there had been an invasion scare in southern California earlier in 1942 . Hubbard claimed to have " definitely sunk , beyond doubt " one submarine and critically damaged another . His view was not shared by his superiors . After reviewing the action reports and interviewing Hubbard and the other commanders present , Admiral Frank Jack Fletcher noted : " An analysis of all reports convinces me that there was no submarine in the area . Lieutenant Commander Sullivan states that he was unable to obtain any evidence of a submarine except one bubble of air which is unexplained except by turbulence of water due to a depth charge explosion . The Commanding Officers of all ships except the PC @-@ 815 state they had no evidence of a submarine and do not think a submarine was in the area . " Fletcher also noted that there was a " known magnetic deposit in the area in which depth charges were dropped . " The clear implication was that Hubbard had been targeting the deposit all along . 
