For 15 Years Sweden Thought Enemy Submarines Were Invading Its Territory. It Turned Out To Be Herring Farts.
In the early 80's after a Soviet Sub ran aground on the South Coast of Sweden, and war return to Russia, the Swedes started picking up elusive underwater signals and sounds. In 1982, several of Sweden's subs, boats, and helicopters pursued one of these unidentified sources
for a whole month, only to come up empty-handed. This continued for over a decade. Every time they picked up an acoustic signal they would search and find nothing but for a few bubbles on the sea's surface. Sweden was, of course, worried about the intrusions, and couldn't think why, with the Cold War now over, Russia would continue to provoke them in this manner.
The Swedes brought in a professor to study the sounds. He and a colleague began the task of figuring out what could be making bubbles on a scale that would make Sweden think it was dealing with a nuclear submarine. "It turns out herring have a swim bladder... and this swim bladder is connected to the anal duct of the fish," Wahlberg said. "It's a very unique connection, only found in herring. So a herring can squeeze its swim bladder, and that way it can blurt out a small number of bubbles through the anal opening."
In layman's terms, they
let one rip. Herrings swim in gigantic schools that can reach several square kilometers and up to 20 meters (65 feet) deep. When something near them frightens them – say, a hungry school of mackerel or a submarine on the lookout for Russian spies – they can generate a lot of gas.
https://www.iflscience.com/plants-an...herring-farts/
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