Prior to 2020, the primary mission of the ship, which was fully funded by Allen's estate, was to explore historically significant wrecks at challenging depths and conditions. A precondition set by Allen was for discovered wrecks to be respected as
war graves and their locations kept secret, known to only national governments and museums. In the
PBS documentary USS Indianapolis Live from the Deep, Allen said, "We've done a number of these explorations to try to find sunken warships. We try to do these both as really exciting examples of underwater archaeology and as tributes to the brave men [who] went down on these ships".
Petrels other mission profile included hosting scientific projects under Allen's mother company,
Vulcan Inc. Petrel explorations were coordinated with organizations around the world. For
United States Navy wrecks, the team collaborated with the
Naval History and Heritage Command. In the Philippines, the crew worked with the National Museum and the Battle of Surigao Strait Memorial Council. In 2018,
Petrel worked with
Australian National Maritime Museum to explore . Robert Kraft, who served as subsea director for Allen, and Paul Mayer,
Petrels lead researcher, traveled to Japan to hand over
ROV video of
Imperial Japanese Navy wrecks to the
Yamato Museum. The project crew was aboard Allen's operating the
megayacht's crewed-submersible
Pagoo, Argus 3000
remotely operated vehicle (ROV) and Bluefin 12D
autonomous underwater vehicle (AUV). The 20 civilian marine crew and 10 project crew worked on 12-hour shifts aboard
Petrel. The project crew consisted of Kraft the expedition leader, Mayer as lead researcher, four ROV pilots and technicians, one AUV specialist, one multibeam surveyor, one videographer, and one systems support engineer. For each expedition, local historians, scientists, and observers complemented the project crew.
Musashi After several years of searching, the same team discovered the in March 2015.
HMS Hood bell recovery In August 2015, the team recovered the bell of after obtaining license from the
UK Ministry of Defence. The recovery of the bell was performed upon the request of the HMS
Hood Association. Only three of HMS
Hoods crew survived and it was the wish of one of them to recover ship's bell as a memorial to shipmates. The bell from HMS
Hood was unveiled by the
Princess Royal on 24 May 2016 to mark the 75th anniversary of the
Royal Navy's largest loss of life (1,415 sailors) from a single vessel.
Malta wreck mapping While on board
Octopus, the project crew deployed a
Bluefin 12D AUV and mapped of seabed around
Malta in September 2015. Sonar images of shipwrecks, several aircraft,
torpedoes, and debris field were captured by the AUV.
Ship details Following the
Musashi discovery and the
Hood expedition in 2015, Allen bought
Petrel in 2016, refitting her as a dedicated research and exploration platform.
Petrel expeditions in 2017 Artigliere Petrel found the Italian Regia Marina
World War II destroyer in March 2017.
USS Indianapolis Petrel found in August 2017.
Indianapolis was located on 19 August 2017 at a depth of in the Philippine Sea. The discovery introduced
Petrel as Paul Allen's newest addition to his expedition fleet. Kraft said of the elusive
Indianapolis, "We did 18 search grids, each one is about a 120 square kilometers and that took us the course of a couple of months. It was about 26 days of searching".
Surigao Strait After discovering USS
Indianapolis,
Petrel sailed to
Surigao City in October 2017 to participate in the 73rd commemoration of the
Battle of Surigao Strait. In November 2017, after gaining approval from the Philippines' National Museum,
Petrel surveyed
Surigao Strait and discovered the wrecks of the Japanese battleships , , and the destroyers , , and . Each one was investigated by the ship's ROV and an onboard local historian confirmed the identity of the wreck.
Ormoc Bay and USS Ward In December 2017,
Petrel explored
Ormoc Bay and discovered the wrecks of the American destroyers , , the , and what is believed to be two s. The discovery of the wreck of USS
Ward was a central theme for the 76th commemoration of the
Attack on Pearl Harbor on 7 December.
Petrel expeditions in 2018 Return to Ormoc Bay In early January 2018,
Petrel returned to Ormoc Bay and dived one of the
Yūgumo-class destroyers found in 2017. Based on the guns and armament configuration, she was identified to be . The identification also validated the final resting places of the other ships of the lost Japanese convoy TA-4: the destroyers , and . The convoy was attacked by aircraft from
Task Force 38 in the
Battle of Ormoc Bay.
Petrel and
Octopus also dove their crewed submersible
Pagoo on USS
Cooper. C-2A Greyhound in the Philippine Sea In February 2018,
Petrel, with a US Navy team aboard, located and mapped the wreckage of a
Grumman C-2 Greyhound aircraft that crashed into the
Philippine Sea en route to on 22 November 2017.
USS Lexington in the Coral Sea On 4 March 2018,
Petrel explored the
Coral Sea and discovered the wreck of the aircraft carrier , which sank during the
Battle of the Coral Sea.
USS Juneau On 17 March 2018,
Petrel located the wreck of the antiaircraft light cruiser .
Juneau was sunk by the in the aftermath of the first
Naval Battle of Guadalcanal, sinking with the loss of 687 men, which included the five
Sullivan brothers.
USS Helena On 11 April 2018,
Petrel located the wreck of the light cruiser .
Helena was sunk during the
Battle of Kula Gulf in 1943 by three torpedoes fired from a Japanese destroyer with a loss of 168 of her crew.
HMAS AE1 The
Royal Australian Navy's submarine , which was lost at sea with all hands on 14 September 1914, and only discovered in December 2017 on the seafloor off the
Duke of York Islands in
Papua New Guinea (PNG), was visited by
Petrels ROV.
Petrels crew devised a close-up camera to view details inside the torpedo tube and engine telegraph. This exploration published on 23 April 2018, was supervised by Find AE1 Ltd in partnership with the Australian National Maritime Museum, the Royal Australian Navy,
Curtin University, the
Western Australian Museum, and the Submarine Institute of Australia. The approval for the survey was granted by
Papua New Guinea National Museum and Art Gallery.
Petrel expeditions in 2019 Niizuki Petrel found the wreck of the upright in of water in January 2019. While the wreck was heavily damaged, her mast is still attached and complete. The find of
Niizuki was noteworthy because she was credited for sinking with the longest torpedo shot ever, with estimates ranging from .
Niizukis discovery is also noteworthy as the photos of the wreck are the first photos of the ship to exist; no photos of her in service are known to have been taken.
Jintsū In February 2019, the 's wreckage was discovered by
Petrel near the mouth of Kula Gulf in the Solomon Islands. The broken cruiser rests in of water. Her bow section is lying on its port side and the stern section is upright.
Hiei On 6 February 2019, the discovery of the was announced, the first Japanese battleship sunk in World War II. According to
Petrel,
Hiei now lies upside down in of water northwest of
Savo Island in the Solomon Islands.
Hiei is the fourth Japanese battleship found by
Petrels crew. The was found in March 2015, and the s and were found in November 2017.
Petrel was also able to survey another , , in a separate mission. Lead researcher Paul Mayer said that
Hiei lies away from
Kirishima.
USS Hornet On 12 February 2019, the crew announced they had located the wreck of the aircraft carrier at a depth of more than off the Solomon Islands. She is in remarkably good condition. She sits right-side up with her island still in place. A portion of her flight deck has collapsed due to the fire that raged on her decks during the battle. A portion of her stern is torn away, but the hull remains mostly intact. Several aircraft are scattered among the wreck.
USS Strong On 26 February 2019, the crew announced they had located the wreck of the destroyer , resting at a depth of . She rests in pieces, the largest of which is the heavily damaged forward section of the ship lying on its port side. The rest of the ship was largely fragmented by the detonation of her depth charges and lies in a compact debris field that includes the ship's boilers, propellers, and wheelhouse.
USS Wasp On 13 March 2019, the crew announced they had located the wreck of the aircraft carrier, resting at a depth of . The ship sits upright, though appears to have broken in two places, just forward and just aft of the island, apparently on impact with the seabed. The island itself is still in place, though the funnel structure was ripped off during the sinking. Several aircraft were also found in the debris field, including Dauntlesses and Avengers.
Furutaka On 4 May 2019, the crew announced they had located the wreck of the Japanese heavy cruiser at a depth of . She lies in two sections, with the bow sitting near the main part of the wreck, which is upright and the bridge is about away.
Maya On 1 July 2019, it was announced that the wreck of the had been found off the coast of the Philippine island of
Palawan. She is mostly intact, with the exception of her forward bow, which broke off and is lying upside down just astern of the rest of the ship. Her bridge and guns are also intact. She lies in of water.
Mogami On 9 September 2019, it was announced that the wreck of the had been found in the
Bohol Sea. She lies mostly intact, with the exception of her bow, which has been blown off, but lying nearby. She sits straight side up at a depth of .
USS St. Lo On 10 October 2019, it was announced that the wreck of the
escort carrier, , the first ship to have been sunk by a
kamikaze, had been discovered on 25 May. She lies at a depth of on the edge of the
Philippine Trench off the coast of
Samar. She sits upright relatively intact, with notable battle damage. She is the first escort carrier to have been found.
Kaga On 18 October 2019,
Petrel announced they had discovered the wreck of the , off the coast of
Midway Atoll. She lies right side up, but with heavy battle damage, below the surface. She is the first Japanese aircraft carrier to have been found.
Akagi On 20 October 2019, the director of undersea operations Rob Kraft and Naval History and Heritage Command historian Frank Thompson aboard
Petrel identified the wreck of the using high-frequency sonar. Located north west of
Pearl Harbor, Hawaii,
Akagi was found at a depth of . It is reported that the wreck is upright, on her keel, and is largely intact. Due to damage sustained by the ROV during recovery from the preceding survey of
Kaga, and a number of other factors,
Petrel was unable to conduct a photographic survey of
Akagi.
Chōkai On 26 October 2019, the search team announced they had discovered, on 5 May earlier in the year, the wreck of the on the edge of the
Philippine Deep. She lies upright with her bow section torn off, deep.
USS Johnston On 30 October 2019, it was announced that the wreckage of a destroyer believed to be had been located. She was believed to have been the deepest ever located shipwreck, estimated at deep. Her identity was confirmed on 31 March 2021, when the submersible DSV
Limiting Factor of Caladan Oceanic surveyed and photographed the deeper main wreck. The visible hull number, 557, confirmed the identity of the ship as
Johnston. She sits upright and well-preserved at a depth of . The record was broken when the wreck of
USS Samuel B. Roberts (DE-413) was found the following year, lying at a depth of .
Doña Paz and Vector On 19 December 2019, it was announced that
Petrel had located and surveyed the wrecks of the Philippine ferry, and the oil tanker . Both wrecks were found apart at a depth of in the
Sibuyan Sea. Both wrecks sit right side up and are in good condition.
University of Hawaii's lost ROV ''Luu'kai'' On 24 December 2019, news came out that
Petrel and a team from University of Hawaii School of Ocean and Earth Sciences and Technology (UH-SOEST) located and successfully recovered the latter's lost ROV named ''Luu'kai
north of Oahu at a depth of . The drone had broken its tether and was lost on the ocean floor on 20 July 2019. To retrieve Luu'kai
, the team lowered a lift elevator and Petrel
s ROV worked on the recovery procedure. Luu'kai'' was recovered by the joint team on 29 August 2019.
Petrel expeditions in 2020 Deep Argo floats in the Atlantic Ocean After finding
Kaga and
Akagi,
Petrel crossed the Pacific in the fourth quarter of 2019 and stationed in the Atlantic Ocean to launch Deep
Argo floats beginning January 2020. Through several weeks in January 2020, in the Brazil Basin of the Atlantic,
Petrel and
National Oceanic and Atmospheric Administration (NOAA) deployed a number of standard Navis floats (2000-m profiles), and deep SOLO floats (6000-m profiles). As part of the Deep
Argo project, a multiyear partnership between the NOAA
Pacific Marine Environmental Laboratory (NOAA PMEL) and the Paul G. Allen Family Foundation, the project aimed for a final deployment of Deep Argo floats aboard
Petrel. Thousands of these floats are freely drifting around the globe to measure the temperature, salinity, and turbidity of the upper ocean, at depths down to and deeper to . The Foundation committed $4 million to NOAA to help implement the Deep Argo effort.
Full ocean multi-beam and sub bottom-profiler In June 2020,
Petrel had a Kongsberg EM124 1°x2° full ocean MBES installed. A sub-bottom profiler, a Kongsberg SBP 29 6° system, was also installed on the ship. Both were tested in the Atlantic Ocean, giving detailed bathymetry readings from depths.
Long-term moorage On 11 June 2020, the
Petrels Facebook page announced that the vessel was going to be moored indefinitely. The announcement read: After a
drydocking in
Florida,
Petrel sailed for
Leith, Scotland, on 16 August 2020 and arrived on 3 September to be laid up. ==United States Navy==