The 13th Floor

Cthulhu Lives!: Examining “The Bloop” and Other Mysterious Ocean Sounds

In 1997, a loud ultra-low frequency sound came from deep in the ocean. Occurring in the South Pacific Ocean just west of the southern tip of South America, this strange sound became known as the Bloop. Hydrophones from NOAA (National Oceanic and Atmospheric Administration) picked up the sound all over the ocean, almost immediately unleashing a tidal wave of speculation as to its origin.

The loudest underwater sound ever recorded, the Bloop lasted over a minute. Although its volume is too great to come from any known species, many cryptozoologists theorize that its origin is either a yet-to-be-discovered species or one that was thought to be extinct. One theory is that the sound came from a megalodon, a prehistoric shark that measures over 60 feet in length. While some cryptozoologists have offered up their own hypothetical creatures, including one simply known as “Bloop”, still other theories seem to be more Lovecraftian in nature. When you think big sound and big sea monster, the mind obviously goes to the biggest oceanic mother of them all, The Great Old One, Cthulhu.


The existence of a megalodon, or any other large oceanic creature, is not completely unheard of. After all, 95% of the ocean is unexplored, and it wasn’t until 2004 that we first saw footage of the fabled giant squid. NOAA has offered an explanation that is far from fantasy stating the source of the Bloop is likely a cryoseism, or iceberg quake. This is what happens when large sections of ice break off and fall into the ocean, an indication that the polar ice caps are melting at an alarming rate.

The Bloop isn’t the only sound out there. Hydrophones all over the ocean have been picking up strange and possibly unexplainable sounds for decades.


In 1999, hydrophones picked up a sound that was heard all across the Pacific Ocean. This low frequency moan sounded like the anguished cry of an extremely large creature. However, scientists attribute this sound to ice running along the ocean floor.


Hydrophones have been listening to Upsweep since 1991. This high pitched wail occurs near volcanic activity leading scientist to hypothesize that is might be lava mixing with sea water.

Slow Down

Slow Down was first heard on May 19, 1997. This sound starts high then descends in frequency over the course of seven minutes.  This sound originates from right off the Antarctic Peninsula and was heard by two hydrophones 3,100 miles away from each other.  Scientists believe that this too is ice running along the ocean floor coming to sudden stop.


The Train

The Train sounds like a train whistle from an old steam-powered locomotive. Occurring in the Antarctica’s Ross Sea, the Train is also believed to be ice related.


Scientists believe the culprit behind this sound to be fire rather than ice. NOAA has pinpointed similar sounds to underwater volcanoes erupting.

Although NOAA offers explanations to their causes, these underwater sounds still fuel the imagination. It’s hard not to romanticize the Lovecraftian creatures living in the deepest parts of our oceans, waiting to one day resurface and make their presence known. But until that day, it seems that they’re content to give us the occasional shout out.