I used to think the loudest thing in the ocean was a whale—maybe a sperm whale clicking at some poor squid, or a humpback belting out its eerie song.
Turns out, it’s a shrimp. Not just any shrimp, but the pistol shrimp, a creature roughly two inches long that produces sounds louder than a gunshot—around 210 decibels, which is intense enough to stun prey and, honestly, make you reconsider everything you thought you knew about tiny crustaceans. The pistol shrimp doesn’t make noise by rubbing body parts together or vibrating anything, which is what most sound-producing animals do. Instead, it snaps one oversized claw shut so fast—at speeds approaching 60 miles per hour—that it creates a cavitation bubble in the water. When that bubble collapses, it produces a shockwave and a flash of light called sonoluminescence that lasts less than a billionth of a second. The temperature inside that collapsing bubble? Roughly 4,700 degrees Celsius, give or take, which is nearly as hot as the surface of the sun. The whole thing is over before you’d even notice, but the sound carries.
Wait—maybe I should back up. The claw itself is asymmetrical, with one significantly larger than the other, and it’s this big claw that does all the work. When the shrimp snaps it shut, a plunger on the claw fits into a socket, forcing water out at such velocity that it creates a low-pressure void. That void immediatly collapses in on itself, generating the snap. It’s not the claw hitting anything that makes the sound—it’s the water imploding.
The evolutionary accident that became a weapon nobody expected
Here’s the thing: pistol shrimp probably didn’t evolve this ability to be loud. They evolved it to hunt. The shockwave from the collapsing bubble is strong enough to stun or kill small fish and other prey, which the shrimp then drags back to its burrow. Some species of pistol shrimp live symbiotically with gobies, small fish that act as lookouts while the shrimp digs and maintains their shared home. The goby gets a place to live; the shrimp gets an early warning system. It’s weirdly cooperative for something that spends its days creating underwater explosions.
I guess it makes sense that something so small would need an outsized defense mechanism.
But the noise isn’t just a byproduct—it’s also a deterrent. In colonies of pistol shrimp, which can number in the hundreds, the collective snapping creates a crackling chorus so loud it interferes with submarine sonar. During World War II, submarines would hide near reefs where pistol shrimp were abundant because the constant noise masked their presence from enemy detection equipment. The shrimp were, unintentionally, providing cover for military operations. Even now, researchers studying underwater acoustics have to account for pistol shrimp noise, which can dominate the soundscape in tropical and subtropical waters. It’s not just occasional snapping—it’s constant, overlapping, a wall of sound that makes it hard to pick out anything else.
The physics of a snap that defies what we thought possible
The mechanics of the snap are still being studied, but what we know is striking. The cavitation bubble forms and collapses in about 300 microseconds. The sonoluminescence—the light flash—was only confirmed in the early 2000s, even though people had speculated about it for decades. Researchers used high-speed cameras to capture the event, frame by frame, and saw the tiny burst of light that accompanies the snap. The temperatures reached during bubble collapse are extreme, but they last such a brief moment that the surrounding water doesn’t heat up. It’s a contained explosion, violent and precise.
Why this tiny crustacean might teach us about energy and engineering
Scientists are now looking at pistol shrimp as a model for cavitation engineering—using collapsing bubbles to generate energy or clean surfaces at a microscopic level. The shrimp does it effortlessly, thousands of times a day, with no apparent wear on its claw. Meanwhile, human-made systems that use cavitation often suffer damage from the very forces they’re trying to harness. There’s something elegant about the shrimp’s design, something we haven’t quite figured out how to replicate. Anyway, it’s humbling—a two-inch shrimp solving a physics problem we’re still working on.
