USS Grenadier: Divers Opened A WWII Sub Lost For 76 Years — What Was Found Inside Changed Everything

Added: 2026-05-09

[00:00:00]In October 2019, a Belgian diver named Ben Reymenants dropped into the Strait of Malacca, 80 miles south of Phuket, Thailand, and landed on the conning tower of a submarine that had been missing for 77 years. The submarine was sitting upright on the sandy bottom at 270 ft, draped in ghost nets, the heavy fishing nets that commercial trawlers had lost over decades, snagged on the wreck, abandoned, left to drape the hull like shrouds. The outer casing was gone, stripped away by years of anchors and troll nets catching on the superstructure and tearing it off piece by piece. But, the pressure hull beneath was intact, heavy steel, recognizable.

[00:00:40]The conning tower, the periscope shears, the capstans, the hatches. The hatches were open, every single one of them.

[00:00:48]That detail told Reymenants everything.

[00:00:51]A submarine that sinks in combat has its hatches sealed. The crew closes them to keep the water out. A submarine whose hatches are all open was scuttled.

[00:01:00]The crew opened them deliberately. They flooded their own boat. They chose to sink it, and then they jumped into the ocean and waited to be captured by the enemy. The submarine was USS Grenadier, and the story of how she ended up on the bottom of the Malacca Strait is not a story about a submarine that was destroyed. It is a story about a crew that destroyed their own submarine to keep it out of enemy hands, then spent 2 and 1/2 years in Japanese prisoner of war camps being tortured for information they refused to give. 76 men went into the water. Four died in captivity. 72 came home. But, the man who found the wreck was not a naval historian or a marine archaeologist. He was the diver who had helped rescue 13 boys and their soccer coach from a flooded cave in Thailand the year before. Ben Reymenants had become internationally known during the Tham Luang Cave rescue in 2018. The boys had been trapped for days in a a cave system in northern Thailand. Ray Mcdonald's was one of the expert divers who navigated the submerged passages to reach them. The rescue made global headlines. It made Ray Mcdonald's famous. But before the cave rescue and after it, Ray Mcdonald's was a technical deep sea diver based in Phuket. He had spent years diving in Southeast Asian waters and he had a method for finding wrecks that no marine archaeologist would have thought to use. He talked to fishermen. The Strait of Malacca has been fished for centuries. The bottom is mostly flat sand, featureless. When a trawler drags a heavy net across that seabed and it snags on something, the fisherman remembers the spot. Not because he wants to find the object, because he wants to avoid losing another net. Ray Mcdonald's collected these coordinates from local Thai and Malay fishermen. Odd spots, snag points, places where nets got caught on something that should not have been there. He plotted them on a chart and looked for patterns. One set of coordinates, 80 to 92 miles south of Phuket, showed a consistent snag point that fishermen had been losing nets on for years. The object was large, much larger than the typical debris that accumulates on a tropical seabed. Ray Mcdonald's assembled a team. Lance Horowitz, an Australian New Zealand diver based in Phuket. Jean-Luc Rivoire, a French diver based in Singapore.

[00:03:16]Benoit Laborey, also French, also based in Singapore. Four men, a privately funded expedition that would eventually cost $110,000.

[00:03:26]They deployed aboard the Spirit, a yacht owned by Rivoire and captained by Horowitz. They ran side scan and down scan sonar over the fishermen's coordinates. The sonar returned a silhouette that was unmistakably a ship, not a fishing vessel, not a barge, something much larger with a profile that was long, narrow and cylindrical, the profile of a submarine. To verify the sonar contact, someone had to go down and look at it, and going down to 270 ft in the Strait of Malacca is not recreational diving. It is a technical operation that requires specialized equipment, mixed breathing gases, and the acceptance of risks that most divers would consider unreasonable. At 270 ft, the pressure is roughly nine times atmospheric. Compressed air becomes toxic. The nitrogen causes narcosis, a cognitive impairment that feels like severe intoxication, and can kill you by making you do things underwater that you would never do on the surface. The oxygen becomes poisonous at partial pressures that exceed the body's tolerance. The team used closed-circuit rebreathers that scrubbed the carbon dioxide from their exhaled breath and blended a precise mixture of oxygen, helium, and nitrogen called trimix. The helium replaced the narcotic nitrogen, keeping the divers mentally clear at depth. They used diver propulsion vehicles to move along the 300-ft hull without exhausting themselves against the current. The Malacca Strait currents are severe. Tidal shifts of up to 3 m restricted diving to narrow windows during slack tide. Heavy swells made the surface operations dangerous. Visibility at depth was poor, and the ghost nets that covered the wreck were an entanglement hazard that could trap a diver at 270 ft with limited gas supply and a long decompression obligation ahead of him. On one dive, Rivwoire's propulsion vehicle got caught in the netting at 80 m, an emergency that required him to cut free while managing his breathing gas, his buoyancy, and the current simultaneously. Over 6 months, from October '19 to March 2020, the team made six dives on the wreck. They measured the hull. They photographed the conning tower, the hatches, the torpedo tubes. They compared every dimension against the naval schematics that the United States Navy had provided. The measurements matched a Tambor class submarine exactly. The length, the beam, the spacing of the hatches, the configuration of the conning tower. Only three submarines were recorded as lost in this region during the war. The other two were British boats with completely different profiles. The open hatches confirmed scuttling. The torpedo tubes were open, too. But, the divers had been warned about those. Before the expedition, the team had contacted relatives of the Grenadier's crew. One family member told them something that changed how they approached the wreck.

[00:06:16]The crew had left the torpedoes in the tubes fully armed. A little present for the Japanese in case they tried to salvage the submarine or send divers inside. 77 years later, those torpedoes were presumably still in the tubes. The divers kept their distance. In the debris field near the hull, the team recovered a single artifact, an electrical component heavily encrusted with marine growth. When they cleaned it, they found a stamped inscription, Ohmite Chicago. Ohmite was a manufacturer of power resistors and electrical components that had supplied the United States Navy for decades. An American-made component on a submarine in the Strait of Malacca whose dimensions matched a Tambor class boat.

[00:06:57]Raymentance and his team announced the discovery in September 2020.

[00:07:02]They said they were 95% confident the wreck was USS Grenadier. The data was submitted to the Naval History and Heritage Command for official verification. But, the story of how the Grenadier ended up on the bottom did not start with the discovery. It started two and a half years before the crew jumped into the water. The Grenadier was a Tambor class submarine, 307 feet long, 10 torpedo tubes, 24 torpedoes, built at the Portsmouth Naval Shipyard in Kittery, Maine, laid down in April 1940, launched in November 1940, commissioned on May 1st, 1941, 7 months before Pearl Harbor. Her her war patrols followed the pattern of the entire submarine force.

[00:07:44]Steep learning curve, defective torpedoes, a crew finding its way in a war nobody had trained for. On her second patrol in the spring of '42, the Grenadier scored a kill that was worth more than anyone knew at the time. On May 8th, 1942, the submarine intercepted a southbound convoy and torpedoed the Taiho Maru, >> [music] >> 14,900 tons, two hits, the ship sank. Post-war analysis of Japanese records revealed what was aboard. The Taiho Maru was carrying Japanese scientists, engineers, technicians, and administrators to the East Indies. These were the men who were supposed to run the oil fields and mineral extraction operations that Japan had seized, the human capital required to turn conquest into industrial output.

[00:08:31]The Grenadier sank them, and in doing so, she disrupted the Japanese resource extraction logistics in a way that no amount of conventional shipping attacks could have matched. You can replace a freighter, you cannot quickly replace the specialists who know how to operate the infrastructure the freighter was supplying. The aftermath of the Taiho Maru attack nearly killed the Grenadier.

[00:08:52]Japanese escorts detected the submarine and subjected her to a 23-hour depth charge barrage, over 70 depth charges.

[00:09:01]The lights went out, leaks opened throughout the hull, the superstructure was twisted, a propeller shaft was damaged, causing a loud squeak every time it rotated. In submarine warfare, noise is death. A squeaking propeller shaft is a beacon that tells every sonar operator in the area exactly where you are. The Grenadier spent the rest of that patrol trying to evade while broadcasting her position with every turn of the screw. She survived. She completed five patrols. She earned four battle stars. By early 1943, she was under the command of Lieutenant Commander John Fitzgerald, and she was heading for the Strait of Malacca on her sixth patrol. The patrol began on March 20th, 1943, out of Fremantle, Australia.

[00:09:45]The hunting was poor. By mid-April, the Grenadier was patrolling along the Malay and Thai coasts without finding significant targets. On the night of April 20th, Fitzgerald spotted two Japanese merchantmen. He tried to close for an attack, but the ships turned away. He calculated their base course and speed, plotted an intercept, and decided to run on the surface at dawn to get into firing position. Running on the surface at dawn in waters patrolled by Japanese aircraft was a calculated risk.

[00:10:14]The submarine's surface speed was faster than its submerged speed. If Fitzgerald could get ahead of the convoy on the surface and then dive for the attack, the geometry would work. The geometry worked. The timing did not. As dawn broke on April 21st, the Grenadier was on the surface. A Japanese patrol aircraft appeared simultaneously. The submarine was spotted. Fitzgerald ordered an emergency crash dive. The submarine was passing through 120 to 130 ft when the bombs hit.

[00:10:45]Two detonations, close aboard. The concussive force heeled the submarine 15 to 20°. Every light went out. Every electrical system failed. The propulsion died. The Grenadier was blind, powerless, and sinking. She hit the bottom at 267 to 270 ft, 17 ft past her rated test depth of 250 ft. The hull held, barely. The Grenadier was now sitting on the ocean floor in a region of the Strait of Malacca where the bottom was soft mud and sand, surrounded by Japanese-controlled waters with no power, no propulsion, and no way to communicate with anyone. The crew was alive, but alive on the bottom of the ocean in a dead submarine is not a condition that remains stable for long.

[00:11:32]For the next 13 hours, 76 men were entombed in a steel tube on the floor of the Strait of Malacca. No power. The electrical systems had been destroyed by the bomb concussions. No lights except the dim yellow glow of emergency battle lanterns, handheld flashlights that cast narrow beams through compartments designed for fluorescent lighting. Every shadow was deep. Every sound was amplified by the steel walls. No propulsion. The electric motors were dead. The diesel engines could not run submerged because they consumed oxygen that the crew needed to breathe. No ventilation. The fans that circulated air through the submarine and scrubbed carbon dioxide required electricity that no longer existed. The air that 76 men were breathing was the air that was inside the hull when the power died. It was not being refreshed. It was being consumed. Flooding in the after compartments. Seawater was entering around the after bulkhead forged ring and through cracks in the hull opened by the bomb concussions. The water was rising slowly, but in a submarine, slowly is fast enough. An electrical fire had ignited in the maneuvering room. The control cubicle, where the switches and bus bars that connected the batteries to the motors were located, was burning. The fire generated toxic smoke that spread through the submarine in the absence of ventilation, filling the compartments with a chemical haze that burned the eyes and throat. The temperature inside the hull climbed steadily. 76 human bodies generate heat.

[00:13:03]In a sealed steel container with no ventilation, that heat accumulates. The residual warmth of the machinery, the batteries, the electrical systems that had been running before the power failed, added to the thermal load. The humidity reached 100%. The air became a physical weight, thick and wet and hot enough to cause the human body to lose its ability to regulate its own temperature. Men collapsed. Heat exhaustion dropped them where they stood. The ones who fell had to be dragged clear of the working spaces by the ones who hadn't fallen yet. The line between conscious and unconscious was the line between working and not working, and that line determined whether the submarine would ever move again. The men who stayed on their feet formed a bucket brigade, hand over hand passing containers of seawater from the flooding compartments upward through the submarine, trying to keep the water level below the electric motors. If the water reached the motors, the last possibility of restoring propulsion would be gone. Others jury-rigged a pump from whatever materials they could find, improvised engineering in the dark at 270 ft in toxic air by men who were losing the ability to think clearly. The electricians worked for 13 hours straight in the dark by touch, tracing wiring runs with their fingers, identifying components by shape and position from memory, trying to restore enough electrical functionality to turn a propeller shaft one more time. At dusk on April 21st, 13 hours after hitting the bottom, they managed to blow the ballast tanks. Compressed air forced the water out. The submarine broke the suction of the mud and rose to the surface. They vented the toxic atmosphere. They opened hatches and breathed. They continued working through the night, but the damage was permanent.

[00:14:50]They got one propeller shaft turning, but it moved too slowly to provide meaningful propulsion or steering. The Grenadier was adrift on the surface in Japanese controlled waters, unable to dive, unable to run, a 300-ft target that could not move. Dawn on April 22nd, two Japanese vessels appeared on the horizon, an armed merchantman and an escort ship, closing fast. An aircraft ascended from above. Fitzgerald looked at what he had, a submarine that could not dive, could not maneuver, and could not outrun anything. A crew that had spent 13 hours in the dark on the ocean floor and a night on the surface trying to fix a boat that could not be fixed.

[00:15:32]He made two decisions simultaneously.

[00:15:35]First, fight on the surface as long as possible. The crew manned the deck guns and the anti-aircraft weapons. When the Japanese aircraft made its attack run, the Grenadier's gunners opened fire and hit the plane on its second pass. The aircraft broke away, damaged, but dropped a torpedo that detonated 200 yards from the submarine. Second, scuttle.

[00:15:56]>> [music] >> While the guns were firing, the crew began destroying everything classified aboard. The torpedo data computer, one of the most sensitive pieces of technology in the American arsenal, was shot to pieces with a Thompson submachine gun. The radio equipment was smashed with hammers. The encoding machines were destroyed. The codebooks and cryptographic documents were stuffed into weighted bags and thrown into the deep water of the strait. Then they armed the remaining torpedoes in the tubes, left them loaded, left the outer doors open, a final gesture of defiance.

[00:16:28]If the Japanese tried to board or salvage the submarine, the torpedoes would be waiting. The crew opened the main ballast tank vents. They opened every hatch. They flooded the submarine deliberately and watched her sink. Then 76 men jumped into the Strait of Malacca and waited for the Japanese to pick them up. The Japanese merchantmen collected them from the water. They were taken to Penang, registered as prisoners of war, photographed, cataloged, and for the next 2 and 1/2 years, they entered a system that was designed not to hold them, but to break them. The Japanese military viewed surrender as a violation of the Bushido code. In the Japanese warrior tradition, a soldier who surrendered had chosen dishonor over death. He had forfeited his status as a combatant and his dignity as a human being. The treatment of prisoners reflected this belief at every level, from the camp commandants who authorized the brutality to the guards who carried it out. The Grenadier's crew was separated and moved through transit camps along the Malay Peninsula. The camps were overcrowded, the food was insufficient to sustain human health, the medical care was nonexistent, disease spread through the camps with the inevitability of weather.

[00:17:39]Eventually, the men were loaded onto transport ships. The prisoners called them hell ships. The holds were packed with men standing shoulder to shoulder in darkness without sanitation, without adequate water, in temperatures that caused men to pass out and die where they stood. The ships were unmarked as prisoner transports. American submarines, not knowing what was inside, torpedoed some of them. The Grenadier's crew survived the transit. They ended up at Fukuoka Camp number three near Yawata on the island of Kyushu. The interrogators wanted technical information, submarine depth capabilities, radar frequencies, sonar performance specifications, the technology that made American submarines the most effective weapons in the Pacific. This was information that could save Japanese ships and kill American submarines. The stakes were not abstract. The methods were not subtle.

[00:18:30]The men were beaten with clubs, penknife blades were forced under their fingernails, they were subjected to stress positions, sleep deprivation, starvation, and psychological degradation designed to erode the boundary between endurance and compliance. The crew of the Grenadier gave them nothing. 76 men, starving, [music] beaten, sick, held in conditions designed to degrade every aspect of human dignity, refused to provide actionable intelligence to their captors. Not one man broke. Not one piece of information about American submarine technology reached Japanese intelligence through the Grenadier's crew. One survivor managed to construct a diary from scrap cardboard and paper.

[00:19:12]He recorded the names of his fellow prisoners. He documented their daily experiences. A piece of evidence that should not have existed, created in a place designed to erase identity. Four men did not survive. Motor machinist's mate Charles Doyle, steward's mate Justiano Garcia Guico, machinist's mate Charles Linda, machinist's mate George Snyder Jr. They died of disease, malnutrition, and the complete absence of medical care. The Navy presumed the entire crew was dead. It was not until November 27th, 1943, 7 months after the sinking, that word reached Allied forces in Australia that survivors existed. The remaining 72 men, including Commander Fitzgerald, were liberated at the end of the war in August 1945. They came home.

[00:20:00]They carried the physical and psychological damage of 2 and 1/2 years in Japanese captivity for the rest of their lives. The submarine they had scuttled remained on the ocean floor, unseen, unvisited, slowly being buried under decades of fishing nets and troll damage. The outer casing torn away by anchors, the pressure hull exposed, the hatches still open, the torpedoes presumably still armed. For 77 years, nobody knew exactly where the Grenadier was. The Navy knew the general area, the Strait of Malacca off the Malay Peninsula near Penang, but the strait is vast and the bottom is sand and the submarine left no marker on the surface when she went down. The fishermen knew something was there. Their nets kept snagging. They marked the spots on their charts and avoided them. The coordinates sat in their logbooks and their memories for decades, known to the men who worked the water, but invisible to the historians who studied the war, until Remnants asked the right question.

[00:20:58]"Where do you lose your nets?" The answer pointed to a patch of seabed 80 miles south of Phuket. The sonar confirmed a submarine-shaped object. Six dives over six months confirmed the identity. The measurements matched, the hatches were open, the ohmite resistor was American, the location matched the historical record, USS Grenadier, found not by military sonar or government-funded search teams, but by four divers on a yacht, guided by fishermen who had been losing nets on a dead submarine for years. Under the Sunken Military Craft Act, the wreck is the sovereign property of the United States government. It is a protected site. The exact coordinates have been withheld to prevent salvage or disturbance. The torpedoes in the tubes, if they are still functional after 77 years in salt water, ensure that anyone who attempts to enter the hull is taking a risk that the crew of the Grenadier intended. The Grenadier is not a war grave in the traditional sense. Nobody is inside. The crew survived the sinking. They jumped into the water and were captured. The four men who died perished in camps on land, not in the submarine. The wreck is something else.

[00:22:07]It is the physical evidence of a choice, the choice to destroy your own ship rather than let it fall into enemy hands. The choice to shoot the fire control computer with a submachine gun.

[00:22:18]The choice to smash the radios and burn the code books. The choice to arm the torpedoes and leave them as a trap, and then the choice to jump into the ocean unarmed in enemy waters and surrender to a military that regarded surrender as the lowest form of human behavior. 76 men made that choice on the morning of April 22nd, 1943.

[00:22:39]They spent the next two and a half years paying for it in ways that no military training can prepare a person for. 72 of them survived. They came home with scars that the Navy could not see and memories that the Navy did not ask about. They lived the rest of their lives knowing that they had endured something that most people could not imagine and that they had given the Japanese exactly nothing in return. The submarine they left behind sits upright on the sandy bottom of the Malacca Strait, 270 ft down. Ghost nets draped across the conning tower, hatches open, torpedoes armed. An artificial reef now, teeming with marine life that has colonized the steel hull and turned a weapon of war into an ecosystem. The fishermen still avoid the spot. Their nets still snag, and the submarine that Commander Fitzgerald ordered destroyed on the morning of April 22nd, 1943, is still there, still open, still armed, still keeping its secrets in the dark water between Thailand and Malaysia. The crew gave the Japanese nothing. The ocean has given back even less. And the hatches that 76 men opened before they jumped remain open, exactly as they left them 77 years ago.