Is the Bloop Real? The Ocean's Loudest Mystery Explained

In the summer of 1997, researchers at the National Oceanic and Atmospheric Administration (NOAA) were monitoring underwater volcanic activity in the southern Pacific Ocean when they picked up something extraordinary. Their hydrophones — underwater microphones placed more than 3,200 kilometers apart — all recorded the same sound: a massive, ultra-low-frequency rumble that was unlike anything they had ever heard.

They called it the Bloop.

What Did the Bloop Sound Like?

The original Bloop was an extremely powerful underwater sound that lasted about one minute. When sped up 16x to make it audible to human ears, it sounds like a deep, resonant "bloop" — hence the name. The sound was so loud that it was detected by sensors over 5,000 kilometers away.

To put this in perspective: the blue whale — the loudest known animal on Earth — can produce calls of up to 188 decibels. The Bloop was several times louder than even a blue whale's call.

The Sea Monster Theory

When the Bloop was first analyzed, NOAA scientists noted that its audio profile roughly resembled sounds made by living creatures. This observation, combined with the sound's extraordinary volume, led to wild speculation: could there be an undiscovered marine animal massive enough to produce such a sound?

The internet ran with this theory. The Bloop became linked to H.P. Lovecraft's Cthulhu — partly because the sound's origin point (50°S, 100°W) is remarkably close to the fictional location of R'lyeh, Cthulhu's sunken city, in Lovecraft's stories. Conspiracy theorists and cryptozoology enthusiasts embraced the idea of a colossal, unknown deep-sea creature.

What Actually Caused the Bloop

By 2012, NOAA scientists had their answer. After years of analysis and comparison with other recorded ocean sounds, they concluded that the Bloop was consistent with ice calving — the process of large icebergs cracking and breaking away from Antarctic glaciers.

These "icequakes" (technically called cryoseisms) can produce enormously powerful sounds that travel vast distances through the ocean. The sound's characteristics matched recordings of known ice-related events from the Antarctic region, which is relatively close to where the Bloop was recorded.

Other Mysterious Ocean Sounds

The Bloop wasn't the only unexplained sound NOAA recorded in the late 1990s. Other mysterious underwater sounds were given names like "Slow Down," "Julia," "Train," and "Upsweep." Most have since been attributed to ice-related phenomena, but Upsweep — first detected in 1991 and still recorded today — remains partially unexplained, though it's believed to originate from underwater volcanic activity.

Our Verdict

The Bloop is real — it was genuinely recorded by NOAA hydrophones in 1997, and the recording is publicly available. However, the popular theory that it came from a giant sea creature is false. NOAA has conclusively attributed the sound to an iceberg breaking apart in the Antarctic. While the mystery was exciting while it lasted, the scientific explanation is just as fascinating: the immense power of glacial ice is capable of producing sounds that dwarf the loudest animals on Earth.