I-33 was an Imperial Japanese Navy B1 type submarine. Completed and commissioned in 1942, she served in World War II, making one war patrol that included the Battle of the Eastern Solomons, before sinking accidentally in September 1942. Refloated and repaired, she sank again in a diving accident during post-repair sea trials in June 1944. Construction and commissioning I-33 was laid down on 21 February 1940 by Mitsubishi with the name Submarine No. 152. Renamed I-41 on 25 March 1941, she was launched on 1 May 1941. Renamed I-33 on 1 November 1941, she was completed and commissioned on 10 June 1942. Service history Upon commissioning, I-33 was attached to the Kure Naval District and assigned to Submarine Division 15 in Submarine Squadron 1 along with the submarines and . First war patrol The Guadalcanal campaign began on 7 August 1942 with U.S. amphibious landings on Guadalcanal, Tulagi, Florida Island, Gavutu, and Tanambogo in the southeastern Solomon Islands. I-33 got underway from Kure on 15 August 1942 bound for a war patrol in the Solomons area, where she took up a position as part of submarine picket line south of San Cristobal. The two-day Battle of the Eastern Solomons began on 24 August 1942, and she was on the surface that day heading for a new position when a United States Navy SBD-3 Dauntless dive bomber from the aircraft carrier attacked her at 11:05 at , but she crash-dived and avoided damage. She sighted a U.S. task force on 30 August 1942 but was unable to get into a position to attack it. She departed her patrol area on 20 September 1942 bound for Truk, which she reached on 25 September 1942. Sinking at Truk On 26 September 1942, I-33 was at Truk tied up alongside the 6th Fleet repair ship Urakami Maru with her stern moored to a wharf on Dublon. Half of her crew was ashore on leave, her commanding officer was aboard Urakami Maru, and her navigation officer was the senior officer on board. Early in the morning, I-33 crew members and three engineers from Urakami Maru began repairs to I-33′s No. 6 torpedo tube, one of the lowermost tubes. At 09:21 the navigation officer allowed the crew to open the drain cock of the aft main ballast tank in an attempt to make the repairs easier by reducing the effect of swells in the lagoon on