Imperial Japanese Navy (IJN) Akagi 赤城 was a Japanese aircraft carrier that was in service from 1927 to 1942. It was originally designed as an Amagi-Class battlecruiser, but construction as such was not finished due to the 1922 signing of the Washington Naval Treaty. In 1927, the incomplete hull of Akagi was repurposed and used to build a larger and faster aircraft carrier.

Akagi had an overall length of 261 meters, a beam of 31 meters, a draft of 8 meters, a maximum speed of 31.5 knots, and a range of 12,000 miles at 16 knots. It had a complement of 1,630 personnel and 88 aircraft.

Akagi was Japan’s flagship for the Kidō Butai or “Mobile Force” in the Pacific Theater. It took part in several operations during World War II, including the attack on Pearl Harbor on December 7, 1941, the Battle of Rabaul (New Guinea) on January 20, 1942, the Indian Ocean raid from March 31 to April 10, 1942, and the Battle of Midway from June 4-7, 1942. During the Battle of Midway, three Douglas SBD Dauntlesses from USS Enterprise targeted Akagi. One of these was piloted by Lieutenant Commander Dick Best, who struck Akagi with a 1,000 lb bomb at the middle elevator for the upper hangar deck, causing a chain of explosions. Akagi soon became inoperable, and on June 5, 1942, Admiral Yamamoto ordered the carrier to be scuttled. Destroyers Arashi, Hagikaze, Maikaze, and Nowaki each fired torpedoes into Akagi, sinking the carrier.

On September 10, 2023, Ocean Exploration Trust and partners surveyed Akagi during the Ala ‘Aumoana Kai Uli expedition, which was funded by NOAA Ocean Exploration via the Ocean Exploration Cooperative Institute. At the time, Akagi was intact, but severely disarticulated, and embedded in seafloor sediment. A large section aft of amidships was damaged, likely caused by bomb damage and a subsequent chain of explosions. The deck on the starboard side slopes downward, indicative of where the exhaust port would have been.

18 hours of video was collected of Akagi using remotely operated vehicle Atalanta. The video was processed into still images and color corrected using Adobe Photoshop 2024. 9,097 images were used to create 17 photo models of the site: portions of the starboard side (5), portions of the port side (2), deck structures (3), stern (3), bow (1), and debris field along the port side of the site (3). Due to distortion of some of the models and quality issues, only 10 photo models were aligned in Rhinoceros 8 and uploaded to Construkted Reality.

A full annotated video of this dive can be viewed on SeaTube.

Site Name: IJN Akagi

Type: UCH

UCH Vessel Date Built: March 25, 1927

UCH Vessel Date Sank: June 5, 1942

Hull Material: Steel

Official Number: N/A

Expedition Number: NA154

Expedition Name: Ala ‘Aumoana Kai Uli

ROV Dive Number: T1002

ROV Dive Date: September 10, 2023

Location: Hawai‘i

Depth: 5 kilometers

Length: 261.21 meters

Width: 31 meters

ROV Used: Atalanta

Camera Information: Insite Mini-Zeus HD

Video or Stills: Video

Number of Images Used/Format: 9,097/JPG

Image Alignment Percentage: 86%

Number of Tie Points: 1,152,584

Link to Raw Video Footage: Link to come

Time to Complete: 64 hours

Orthomosaic Views Available: No

Images Available: Yes

Animations Available: Yes

Available File Exports/Location/POC:

Link to NOAA Ocean Exploration Project Page:

Software: Agisoft Metashape Professional Version 2.1.0, Rhinoceros 8

Developer: Raymond Phipps, NOAA Ocean Exploration explorer-in-training, April 26, 2024.

Credit: Model courtesy of NOAA Ocean Exploration, Ala ‘Aumoana Kai Uli expedition.