After Hubbard was removed from command for conducting unauthorized gunnery practice in Mexican territorial waters, the PC-815 served as a shore patrol vessel off San Diego, California.

[4] In the early hours of 19 May 1943, the crew of PC-815 detected what Hubbard thought was first one, then later two Imperial Japanese Navy submarines approximately 10 nautical miles (19 km) off the shore of Cape Lookout, Oregon.

However, the subsequent investigation by the Commander NW Sea Frontier, Vice Admiral Frank Jack Fletcher, cast a skeptical light on Hubbard's claims.

Both he and Tom Moulton, one of his officers, claimed that the official denials of any Japanese submarine presence off the Pacific coast had been motivated by a desire to avoid panic among the U.S.

The I-176 was sunk in the Coral Sea in May 1944 and removed from the Japanese Navy List on 10 July 1944 – a year after Hubbard was relieved of command of the PC-815.

Hubbard took the opportunity to order an impromptu gunnery exercise while anchored just off the Mexican territory of South Coronado Island, to the south-west of San Diego.

It concluded that Hubbard had disregarded orders, both by conducting gunnery practice and by anchoring in Mexican territorial waters without proper authority.

[citation needed] Vice Admiral Fletcher, who both chaired the board and read the prior after action report, rated Hubbard "below average" and noted: "Consider this officer lacking in the essential qualities of judgment, leadership and cooperation.

According to her Movement Card she took part in the occasional offshore patrol, participated in training exercises, and escorted submarines in and out of the harbor.

[2] Navy divers demolished the wreck in early November 1945 due to the navigation hazard that it posed to a busy shipping channel.