USS Indianapolis Discovered: Analysis of a Shipwreck Site

This is a transcript of a presentation at the Preserving U.S. Military Heritage: World War II to the Cold War, June 4-6, 2019, held in Fredericksburg, TX. Watch a non-audio described version of the presentation on YouTube.

USS Indianapolis Discovered! Now What?

Presenters: Blair Atcheson and Richard Hulver


The 2017 discovery of USS Indianapolis (CA-35), one of the Navy’s most storied ships and sought-after wrecksites, propelled the vessel back into the public eye and highlighted a string of deep-water World War II shipwreck investigations. After the media hype subsided, the Naval History and Heritage Command (NHHC), as managers of the U.S. Navy’s sunken military craft, needed to determine the next steps for Indianapolis, which would inform how we approach similar site discoveries.

NHHC is responsible for the management, research, preservation, and interpretation of the U.S. Navy’s sunken and terrestrial military craft. A collection that includes over 3,000 shipwrecks and 14,000 aircraft wrecks dispersed world-wide and which date from the American Revolution to the nuclear age. These wrecksites are often the final resting places of Sailors and Marines who paid the ultimate sacrifice in service of the nation, carry significant historical importance, and may contain environmental or public safety hazards such as oil or unexploded ordnance. Accordingly, the Navy’s general policy towards these wrecksites are to leave them undisturbed, thereby encouraging in situ preservation and documentation.

Three miles below the surface, Indianapolis is the Navy’s deepest confirmed shipwreck and the incredible state of preservation provides a unique opportunity for research and scientific analysis. The study of Indianapolis also underscores new challenges for submerged cultural resource managers as depth becomes less of a protecting factor and with an increasing interest in deep-water wrecksite tourism. This paper will discuss the NHHC research that helped lead to the discovery of Indianapolis by Paul Allen’s research team, the historical and archaeological analysis of the wrecksite, evolving approaches to deep-water wreck documentation methodology, and current management strategies to preserve and protect the site.

While the discovery of a wrecksite is often considered the “final chapter” in the life of a ship, for NHHC, it is the next chapter in a continuing story. As the Navy’s institutional memory, NHHC is responsible to present the most accurate history possible and to preserve the cultural resources that remain. The study of Indianapolis, a ship that is most often remembered for her worst 10 minutes, ensures that this decorated World War II ship and crew are remembered and honored for their service.

A smiling white woman with long blond hair and glasses wearing a maroon polo shirt and nametag.


Blair Atcheson: I am Blair Atcheson with the Naval History and Heritage Command Underwater Archeology Branch, NHHC for short because that's a mouthful. Myself along with Dr. Richard Hulver, NHHC's lead historian on Indianapolis, have been conducting a review of the wreck site data provided by ocean exploration team Vulcan Inc., funded by the late Paul Allen. I'll be discussing the discovery, the historical analysis, and our site management plans.

To understand what led to the sinking, the Navy's Bureau of Ships, BuShip, interviewed the 316 survivors for their perspectives, recollections of what transpired in the chaotic final minutes of the ship. The official report was filed on October 2nd, 1945. Since there was no wreckage to analyze, the report represented more of an informed estimate than definitive conclusion. The discovery of Indianapolis has provided the Navy with data to reinvestigate the sinking and corroborate the 1945 records with the actual wreckage.

Alittle about Indy. She was basically a big ship but a fast ship with a lot of guns. She was commissioned in 1932 under the restrictions of the Washington Naval Treaty from World War I.

As Dr. Hulver wrote in his book, A Grave Misfortune, which is available to the public, I recommend you go to our website and download it, he says, "Indianapolis was a decorated World War II warship that's primarily remembered for her worst 15 minutes." She has a commendable service record prior to World War II and during the war received 10 battle stars for service in action.

At Okinawa in late March 1945, a kamikaze bomb severely damaged the vessel and required extensive repairs at Mare Island Navy Yard in California. This set Indy on the path to what would be her fatal final mission.

While undergoing repairs at Mare Island Navy Yard, Indy was selected for a top-secret mission to carry components for the A-bomb, Little Boy, to Tinian. They made this successful high-speed trip setting a speed record to Pearl Harbor that has yet to be broken with none of her crew or even her captain knowing what they carried.

Silhouette of navy heavy cruiser USS Indianapolis floating on the ocean.
USS Indianapolis preparing to leave Tinian after delivering atomic bomb components.

Credit Naval History and Heritage Command

On July 28th, 1945 Indy departed Guam for Leyte but just after midnight on July 30th, she was sunk by Japanese submarine I-58. Four days later on August 2nd, the small remainder of her crew were rescued.

As a report on her loss went up the navy's chain of command, one reviewer's comments written on the routing sheet matter-of-factly, summarizes the situation and the new normalcy created by World War II: "Excellent report. She was a good ship. Sorry to lose her."

The story of Indianapolis is not an entirely positive one for the Navy but as the Navy's institutional memory, it is NHHC's responsibility to tell it so that the hard-won and hard-learned lessons of the past are not forgotten, can be utilized to enhance the war fighting effectiveness of today's navy, and honor the sacrifices of the American sailor.

In 2016 the Director of NHHC, retired Admiral Sam Cox, stood up a team of historians, archivists, public affairs officers, and archeologists to make sure that the Navy had an accurate history on the loss of USS Indianapolis that was available to the public.

With the 70th anniversary of the loss, renewed public interest and its history and wreck location, NHHC archeologists and historians were specifically tasked to revisit the sinking. The results came with interesting new conclusions.

The prospective offered by Indy's captain, Charles McVay, formed the foundation of the Navy's damage assessment and sinking location and offered enough detail to be of use to future researchers. He provided a critical clue as to his ship's progress along the route by mentioning the passing of an unidentified LST approximately 11 hours before the sinking.

Seven decades later, Dr. Hulver identified McVay's LST as number 779 and her noon coordinates for July 29th, 1945 place Indianapolis further southwest than historically believed. The coordinates from LST-779 was a key piece of information for the drift modeling being conducted by NHHC, the Naval Historical Foundation and the US Naval Academy. Based on the results, NHHC proposed a 10 by 10 nautical mile survey area approximately 35 nautical miles to the southeast of the navy's 1945 sinking location.

This information was made available to anyone in the public that asked. One of those groups was Paul Allen's company at Vulcan, funded to locate and identify World War II shipwrecks. Independently of NHHC, but with the information on the LST, Vulcan developed their own survey area and located the wreck on August 19th, 2017. The wreck was only six nautical miles outside the navy's proposed new search area.

Over the next year, Vulcan had a string of major World War II US Navy shipwreck discoveries including Juneau, Ward, and Lexington. And this year they have just discovered Wasp and Hornet. The team at Vulcan has been forthcoming, cooperative, and responsible in their approach to locating World War II shipwrecks and desires to get the information to the responsible government agency.

While the discovery of a wreck is often hailed as the final chapter in the story of a ship, for the NHHC Underwater Archeology Branch, this is the first step. We are responsible for the management, analysis, conservation, and preservation of over 18,000 sunken...

Color image in shades of blue and green of metal hull with hole it in resting on ocean floor.
Torpedo impact to the starboard side at frame 46, second deck.

That includes over 18,000 ship and aircraft wrecks from the Revolutionary War through the nuclear age. Vulcan is focused mostly on identification of a wreck, not full documentation analysis, but they generously provide the data collected to NHHC for further study. This data informs our approach to best manage the wreck site as well as other deep-water wrecks. With Indianapolis, we began with a side-by-side historical and archeological review of the wreck data. So, these are preliminary results.

Dr. Hulver indicated five questions from the historical narrative. Does the wreckage give any indications of the ship's movement after the hits? Was the bow severed? How many torpedo hits did I-58 score? Is there evidence of that a Kaiten or a manned torpedo, was used? And does it appear that the magazine exploded?

This is, for those who are familiar, side-scan sonar of the wreck site. And as most of you here are probably familiar, we lack both time and funding. This is my model and in all fairness, this is legitimately what we use to figure out what was going on. Bow, stern.

So, the ship is going along. It is hit on the starboard bow, keel's broken, the bow bends back and rips off. Second hit to starboard, right near in front of the bridge. This severed communications to the bridge and the engine room. Now the engine room is thinking to keep the one working engine going in order to escape the enemy, not knowing this is pushing water into the open bow.

Our ship is going down at the head, listing to starboard, and slowly circling to port ‘til she almost capsizes before going vertical and sinking. And it had a 3.5 mile descent to the bottom, which is exactly what we see on-site.

So, we have the bow at the very... Let's see. Sorry for those of you who are colorblind but here's the bow. Then you have the main hull wreckage, so you can see that came around, circled to port, capsized right about here. The bridge, the 8-inch guns, and some of the hangar debris, and then the main hull.

Color image in shades of blue and green of rectangular opening in metal platform.
Exit blast of the torpedo explosion on the communication platform, frame 46, directly above the initial torpedo contact.

Yes, the wreck site does answer our first question and shows the movements after the hits and it's exactly as the survivors described.

The next question, was the bow severed? Obviously. It is lying on its starboard side half-buried in sediment. You're looking at the [inaudible] deck here, the capstan and anchor chain still in place.

Seaman 1st Class Pena was standing watch on the 20-millimeter guns. The blast threw him up in the air but after collecting himself, he saw the bow was gone forward to frame 10, which that is frame 10. He also made note that four sailors were sleeping on the forward section of the bow and these were likely the first lives lost that evening.

Navy engineers determined that only a charge of 452 pounds was capable of blowing off such a small portion of bow structure. Additionally, the USS Minneapolis, pictured here, corroborated much of what was reported on Indianapolis. Minneapolis lost her bow in 1942 when hit by similar charge of frame 17 first platform.

Now you're looking at the port side. This is the hull number, 35, which identified this as Indianapolis and was the first thing they found. And right behind it, you can't see but there are about eight frames of hull plating bent at a 90 degree angle from the rest of the bow. This supports our theory that the bow's keel was broken first, pushed back along the side of the ship before detaching by the force of the water.

And then the second picture shows the anchor, jack staff still in place. Without question, almost immediately Indianapolis' bow was gone forward to frame 10.

How many torpedo hits did I-58 score? I-58 launched six Type 95 torpedoes at Indy. Captain Hashimoto reported that he heard four hits then up to 10 additional explosions while the ship was sinking. The data confirms the survivor reports of two hits, one at the bowel near frame six and seven at the water line and a second at mid-ship near frame 46.

It’s sinking. So, this is hard to see but it's the best picture I can get. The 35 is up here. The hull plating. This is the explosion damage. This was augmented also by the aviation gasoline fuel tank and the keel is right there.

The second torpedo hit struck in the vicinity of frame 46 slightly below the first platform level just after the number two turret. Damage caused by the second hit was much more widespread than the hit forward and undoubtedly killed numerous crew. There were bunks for over 150 crewmen in the spaces directly above the blast and none of that crew survived.

The damage, however, from the second torpedo seems very modest in comparison to survivor accounts, which discussed ruptured decks with flames coming through scorching hot walls in floors that burned hands and feet. So see here, this is the entrance of the initial torpedo contact, the very top of it.

Then there the blast moved up. So, if you go down in your imagination, the initial contact's here, it goes up. And this is the top of the communications platform. The blast went up, hit the ship's longitudinal bulkhead, which is what Navy engineer's guessed in 1945 based on crew descriptions, and then what we're seeing in the wreck here.

This is the exit blast of the torpedo damage and it engulfed both the bridge and the back of the number two gun in flames. There's a little more. That is the barbette for number two, so where the number two would be gun would be sitting, and the exit blast.

Captain Hashimoto stated that he had the Kaitens, or manned suicide torpedoes, prepared but knew the ship was hit and didn't deploy them. Based on the damage, we cannot determine if a Kaiten was used, nor do we think we would be able to.

The last question, did the magazine explode? As you saw on the previous images, besides those two modest holes, there's no evident damage or severe buckling in the hull plating as we would expect to see if the 8-inch ammo exploded. Granted, we can't see the full extent of damage because it's buried in sediment. It is likely the 5-inch ammo storage exploded.

The wreckage confirms that the Navy's initial investigation taken from survivor accounts and battle damage reports was remarkably accurate. We've seen this with a number of our wreck sites that the survivor accounts, sometimes recorded years after the event, such as USS Houston, is rarely inaccurate. It's a testament to our officers and sailors.

Some site facts and what we've been seeing in the archeological assessment. Right here, what I can only think to describe of as pincers on an insect, is the hull plating being stripped back from the ship as it was sinking by the force of the water.

Here's a view of it. You're looking at starboard side, roughly frame 23, and this is the hull plating that looks like it was just crumbled aluminum, even though it's steel. It's from the starboard, or sorry, this is from port side, looking in. You can see some of the incredible preservation with the two-tone paint. And then here, just because it's amazing to see the teak decking is still so well-preserved.

One of the interesting things we noticed was 12 missing frames of ship. We know several survivors escaped right through here, the hatch at frame 17, so we know it was attached during the initial surface sinking, but is gone in the video data. Survivors did mention that the deck was cracking in the section after the hits, so we believe this area was weakened by the two hits and then as it was sinking to the sea floor, it started to come apart.

In the debris field, we have found some missing frames of ship in this rather large chunk, but that does not equal 12 frames of ship.

This is the stern. Now this stern is really interesting because it is so badly damaged and none of the survivors mentioned damage here and that's where most of the survivors came from. They gathered there amid the chaos and the number three gun was actually the last thing that many of them touched.

You can see behind the gun. It's a little hard to see but the deck has collapsed, the main deck, and here are the quad 44-millimeter guns and the walls are caving in.

In discussions with Navy engineers, we believe this is implosion damage because the crew was able to dog the watertight doors here and the impact with the sea floor.

Here are the guns. We've been able to document and find all three of the eight triple barrel, 8-inch 55 caliber guns. Number one and two fell out when the ship capsized and are buried barrel first in the sediment. We haven't been able to determine which one is which. And then I'll just say that the number three, which is amazingly still in place.

We have all the 5-inch guns are in place except for one, which we believe was knocked off by the catapult as it sank and the quad 44-millimeter guns but none of the 20-millimeter anti-aircraft guns are anywhere on-site and we have not found them in the debris field yet.

Three Curtiss SC1 Seahawks were on board Indianapolis at the time of her loss. Survivor accounts indicate both the catapult and plane it held killed crew before the ship sank. The other two planes likely dumped out of their hangars when the ship went completely vertical prior to sinking.

It's hard to see. This is the hangar deck. Starboard, so that's right there. It's cleared of any debris. And then this is the catapult right there, where one of the plans would have been stored and it has fallen back here on the port side in the pile of debris behind one of the 5-inch guns.

There's a large debris field with aviation-specific material that sits slightly to the northeast of the wreck. In the data available, there's no large portion of an intact aircraft, just these pieces. But these pieces themselves, as you can tell, are phenomenally well-preserved. You can read, well, I can read the bureau number right there, so we knew which aircraft. Because this part was not systematically documented, we aren't able to relate the aircraft pieces. We're not sure how many exactly we found and how they may relate.

Much of the debris field looks like this, with mangled pieces and debris, but we have been able to identify things like gas masks, ropes, peacoats, cups, helmets.

The tripod, forward and aft tripod and masts, they have fallen forward, so they're here kind of in the capsized material. And the forward has fallen, the tripod mass has fallen forward. We're looking at the backside right there. You can see the forward antenna mast, that part is falling backwards and is right next to the ship's bell.

Now most people are more interested in the search and discovery of a shipwreck than the painstakingly slow documentation analysis of wreck site. But that is where we come in for the Navy.

The Indianapolis is a sunken military craft under the jurisdiction of the Department of the Navy and falls under NHHC's management. The site is a fit and final resting place for nearly 300 sailors and a memorial for the over 800 sailors lost at sea. It is incredibly well preserved and we have such a unique opportunity to study and protect the site.

What's next for NHHC and Indy? We need to complete our data analysis report. We would like to create a site plan to the extent the data allows, conduct some flood modeling, and further damage assessment with other Navy commands. As technology improves and more and more deep-water sites are discovered, archeologists are needing to determine the best courses for site management and documentation. For the Sunken Military Craft Act, it's very important that we have a full idea of what's there.

And then some are leading towards photogrammetry to replace the traditional archeological site plan. While we find it is a very important tool, especially for these deep-water sites, that shouldn't replace an archeological site plan.

But this is a challenge when we're getting data from third party researchers and we're receiving terabytes and terabytes of data. It brought to our attention the need to create remotely operated vehicle best practices and guidelines for non-intrusive data collection. We're hoping to have those policies available to the public sometime this year.

Like outer space, the deep ocean is not just for governments and academia anymore. There is an ever-increasing interest in deep-water shipwreck tourism from the seriously privately funded researcher to individuals with submersibles. The site of RMS Titanic has already been impacted by repeated ROV and submersible visits and it will be the site to watch as this industry grows.

Let's see. Based on the knowledge gained from analyzing Indianapolis, NHHC is in a better position to develop policies to address deep-water wreck tourism and to best preserve the Navy's sunken military craft.

Thank you.


Mary Striegel: Okay. Thank you. First question.

Speaker 1: Thank you. That was really interesting and fascinating.

I'm curious in other submerged resources, I'm thinking of previous conflicts, especially the Civil War, there has been recognition of movement of those resources due to water flow, changes in ocean currents, and things of that nature. Is there any evidence of that and if so, are you monitoring that at all or how are you paying attention to that? Or given the condition and weight perhaps of these resources, is that just not an issue?

Blair Atcheson: It's because of the depth. There's no current, so that's why it's such a unique site. We're literally looking exactly what it looked like 73 years ago. So, yeah.

Speaker 2: Is the inaccessibility of the site basically the only thing that's protecting it right now? What did you say, three and a half miles down?

Blair Atcheson: Yes, but that's why we're saying that's not going to last for long, so we're trying to get ahead of the game in that case. And it's also protected by US law, the Sunken Military Craft Act.

Speaker 3: I just wanted to talk about the luck that you have to work on such an amazingly well preserved shipwreck. This does not happen unless it's extremely deep, the reason being that you don't have what we call the concretion forming on the metal, the reaction with the steel does not occur and plus, you've got a fantastic testimony of those wonderful primers and coatings that they were using. But if you were on a much shallower shipwreck, you would not look at the paint the way you look at it here, it's just amazing on all kinds of metals. So, this is another wonderful opportunity to study those shipwrecks.

Speaker 4: Do you know if the Navy has gotten requests for retrieving some of the shallower shipwrecks? I was thinking in the Alaska and the Aleutians and submarines and others that in the Alaska SHPO's office, we've had military veterans interested in military history that would like to retrieve these vessels. Could you speak to the retrieval policy?

Blair Atcheson: Yes. All of the Navy Sunken military craft are protected by the act and there's a permitting program, though, to allow recovery for archeological, educational, and historical purposes. Youu can find out about our permitting program on the website. We released revised regulations in 2016 and so that's the way to request. For Navy authorization, is through our permitting program.

Mary Striegel: And our last question.

Speaker 5: You said that some of the ships may be in danger from the ROVs that are going out there, which is why you're developing a plan. What kind of damages have you seen or do you anticipate from those vehicles?

Blair Atcheson: Anticipate? Well, we know with submersibles, they do release ballast, so making sure that they release ballast away from the wreck site. And with something like Indianapolis, my big concern is the debris field because it's so large and we also, we don't know what's underneath.

Part of it is developing a management plan to determine what research we want to go into to see if we should do a magnetometer survey to see if we can pick up anything under the sediment, what biological samples we might want to take, or paint samples we might want to take.

You can't... Well, I don't want to do that.

But on some of the gun barrels you can see where the sediment settled and we believe that might be the sediment that settled after it sank and caused a huge crater. So, I just imagine that potentially being disturbed. It wouldn't be major. Hopefully, someone well intentioned wouldn't cause major damage. But, yeah.

Mary Striegel: Thank you Blair.

Speaker Bio:

Blair Atcheson is the Program Manager for the Naval History and Heritage Command’s (NHHC) Underwater Archaeology Branch located in Washington DC. Born and raised in Dallas, Blair earned a BA in History from Texas A&M University. Able to combine her interest in military history and shipwrecks, Blair has been at NHHC since 2012. In her current role, Blair administers the permitting program for research directed at U.S. Navy sunken and terrestrial military craft, conducts archaeological research, and specializes in World War II historical research and the development and implementation of historic preservation policy for Navy’s submerged cultural resources.

Last updated: June 2, 2021