On a gray summer day in 1966, Todd Newberry was watching seabirds squabble above the kelp forests of California’s Monterey Bay, when a sailor struck up a conversation that changed his understanding of the Vietnam War. The stranger turned out to be a Navy sonar engineer assigned to the destroyer USS Turner Joy. Just two years prior, Turner Joy, along with USS Maddox, had reportedly been attacked by Vietnamese boats in a mysterious battle known as the Gulf of Tonkin incident. This encounter was pivotal in plunging the United States into the decade-long war that killed 58,000 Americans along with 2.5 million Vietnamese and Southeast Asians. But even today, it’s still not clear whether the Turner Joy and Maddox had actually been under fire.

“He was not supposed to be talking about this stuff, I’m sure,” says Newberry, a professor emeritus of marine biology at the University of California, Santa Cruz who recently recounted this conversation to me. As Newberry tells it, the sonar engineer spoke of strange shapes picked up on the Turner Joy’s sonar displays during the supposed attack. The objects were the size of torpedoes, but they didn’t move like any torpedo the engineer had ever seen before. They seemed to have a will of their own—to come at the ship, then drift right under.

The engineer was convinced that the military had been mistaken about the attack. What they thought were torpedoes, he insisted, were in fact living things.

This story was one that only Newberry and a handful of other biologists in the world could believe. Now 82, Newberry only remembers a little of the conversation—and he has forgotten the sailor’s name. But if it the story is true—and there’s compelling evidence that it is—it may have shed new light on a major incident that escalated to one of the most notorious conflicts in U.S. history. Is it possible that obscure sea creatures helped propel America into  the Vietnam War?

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Near the end of July 1964, the U.S. was stoking conflict with North Vietnam’s communist government by backing covert raids against its radar installations in the Gulf of Tonkin, part of the South China Sea. On August 2, three North Vietnamese boats responded by torpedoing the USS Maddox in broad daylight while the Americans were spying near North Vietnamese islands within the Gulf. Maddox repelled the attack and escaped. Despite the hostilities, the ship was ordered to return to its spy patrols in the Gulf of Tonkin, this time accompanied by a second destroyer, USS Turner Joy.

Two nights after the August 2 attack, a storm struck. The black sea blended with the black sky, obscuring a horizon of heavy waves. Crews aboard the two destroyers thought they detected small, fast-moving vessels that mimicked the attack patterns of the North Vietnamese torpedo boats. For several hours, the two ships defended themselves, performing high-speed evasive maneuvers, firing almost 650 cannon shells and several depth charges into salty darkness.

During the battle, the Maddox crew reported detecting more than 20 torpedoes on sonar. Sailors claimed to have seen enemy cockpit lights, and searchlights across the water. Sonarmen also thought they heard the sound of torpedo propellers over the hydrophones. Turner Joy’s crew reported spotting the wakes of two torpedoes 300 feet off their port side. But when the heat of battle finally subsided, no enemy vessels were accounted for. None were seen retreating; none had been destroyed.

Maddox’s captain, John Herrick, sent a high-priority message to Honolulu within hours, declaring his skepticism that there were any enemies in the first place. “Review of action makes many reported contacts and torpedoes fired appear doubtful,” he wrote. “Freak weather effects on radar and overeager sonarmen may have accounted for many reports. No actual visual sightings by MADDOX. Suggest complete evaluation before any further action taken.”

Nevertheless, the U.S. Secretary of Defense, Robert McNamara, chose aggression over caution: He immediately advised airstrikes against North Vietnam. President Lyndon B. Johnson, who was up for reelection that year, took McNamara’s advice and made a swift public announcement of an “unprovoked attack” in international waters. Three days later, both branches of Congress passed the Gulf of Tonkin Resolution, which gave Johnson near-unlimited authority to deploy U.S. military forces in Southeast Asia. America fully committed to the conflict in Vietnam.

In 2005, the National Security Agency declassified a trove of documents that revealed military communications during the Tonkin incident, leading historians to conclude that there was no second attack on August 4, 1964. The historian Edwin Moïse believes that weather, schools of fish near the surface, birds, or sensor problems caused sailors to misinterpret their instruments.

In the 2003 documentary film Fog of War, Robert McNamara himself said that there was no August 4 attack. President Johnson even said at the time, “For all I know, our navy was shooting at whales out there.” Commander James Stockdale, who had piloted a Navy F-8 Crusader jet over the scene during the supposed counterattack, reported that he “... had the best seat in the house to watch that event and our destroyers were just shooting at phantom targets ... There was nothing there but black water and American firepower.”

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When he ran into the sonarman, Todd Newberry was studying little-known ocean animals called tunicates, or sea squirts, for his Ph.D. work at Stanford University. Upon hearing the story, Newberry recognized rare marine organisms that matched the sonarman’s description. The culprit was an enigmatic cousin of the sea squirts: giant pyrosomes.

Pyrosomes are colonies of clear filter-feeding organisms with a strange life history. Each half-inch long individual pyrosome is tube-shaped and catches floating food as it takes in water at one end and shoots it out the other in a near-continuous jet, allowing it to feed as it swims. Individuals in the colony are stuck together—side-by-side—forming a long blunt-ended tube. With the combined jet propulsion, the whole colony swims steadily along. Pyrosome colonies look, for lack of a more accurate analogy, like a giant swimming condom.

At its largest, a colony of giant pyrosomes can reach up to 60 feet. They live worldwide, in tropical and temperate oceans, and are known to inhabit the Gulf of Tonkin. Moreover, pyrosomes are sometimes found floating in clusters of several colonies near the surface of the ocean at night. The colonies swim much slower than a moving torpedo, but their appearance in a pitched battle could have been very confusing. “These things are the size of torpedoes, so they produce the same [sonar] image,” says Newberry. “It all fit together, as far as the character of the colony and its behavior.”

Pyrosomes are also bioluminescent. Like many organisms in the ocean, each individual pyrosome emits bright pale-blue light when it’s disturbed, and these lights flash through the whole colony. The light is bright enough to induce nearby colonies to flash, too. “I mean they’re really bright!” exclaims Karen Osborn, a research zoologist at the Smithsonian National Museum of Natural History. “Almost bright enough that you can see them in daylight.”

Osborn confirms that the tumult of high-speed warships would be more than enough to set the sea ablaze with flashing pyrosomes—whose name, in fact, is Greek for “fire body.”* “They could certainly have shown up on sonar,” she says. “I can totally see that if you didn’t know that something like them exist and you were looking at them in the water, your imagination could go pretty crazy with what you were seeing.”

“Imagine telling your commander who thinks you’re being attacked by torpedoes, ‘No sir, those are Pyrosoma!’ You’d be put in the brig immediately,” says Newberry. “Here’s an angle that was never picked up at the time. It could be a perfectly natural phenomenon.”

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It was dumb luck that Turner Joy’s sonarman happened to tell this tale to the one person who might understand. Newberry discussed his story with two close friends, the invertebrate biologists John and Vicki Pearse. Years later, the Pearses included the story in a chapter about pyrosomes in their 1987 textbook Living Invertebrates.

Despite being out of date, Living Invertebrates is still a popular teaching tool. These scientists have retold this story of pyrosomes over a half-century of teaching, giving it a life of its own, just like historical accounts of the Gulf of Tonkin incident itself. “It was a misunderstanding by people who had never heard of pyrosomes,” says Newberry. “It’s an irresistible story to bring up.”

In interviews for the documentary of the same name, Robert McNamara describes the “the fog of war”: “War is so complex it’s beyond the ability of the human mind to comprehend all the variables. Our judgment, our understanding, are not adequate. And we kill people unnecessarily.” McNamara may never have considered that one of those variables could be biological.

The ocean is rife with incredible phenomena that sailors have mistaken for threats. Docile manatees were malicious mermaids that lured men at sea to their deaths. Deep-sea oarfish are the spitting-image of sea serpents. The Fata Morgana—a simple mirage—terrified mariners who saw ships over the horizon as ghosts heralding their doom. Newberry’s tale of bright pyrosomes may be the only record of a modern mistake so extreme that it directed the course of war.

* This article originally stated that pyrosome is Latin for "fire body." We regret the error.