25 Deep Sea Mysteries And Oddities That Will Leave You Baffled

Posted by , Updated on May 27, 2015

More humans have walked on the moon than have been to the deepest parts of planet Earth. Covering 70% of Earth’s surface, the oceans are the largest habitat in the world yet we only know around 1% of the seafloor. Many a mystery surrounds the deep blue and in this list we dredge up some of the least understood. Check out these 25 deep sea mysteries and oddities that will leave you baffled!


Giant Oarfish

Giant oarfish

Thought to be the reason for many alleged sea serpent sightings, the giant oarfish can reach up to 36 feet (11m) long – that’s bigger than a shipping container. Previously assumed to be quite rare, these mostly unknown creatures seem to be more common than once thought.


Deepwater Photosynthesis

Marine bacteria

There may be no sunlight at the bottom of the ocean, but some bacteria near hydrothermal vents use the vents’ dim red glow to photosynthesize and produce food for themselves. Scientists are still trying to figure out how it’s all possible.



NOAA Upsweep electrograms

The NOAA listens to sounds from oceans all over the world. Most have been identified, but the sound known as upsweep remains elusive to understand. Upsweep is a few seconds of narrow-band upsweeping sounds and is most active in Spring and Autumn.


Vampire Squid

Vampire squid

The vampire squid is a bizarre creature which produces some of its own light through glowing tentacle tips and spots on its sides. If disturbed, it can eject an ink which glows.


The Baltic Anomaly

Baltic Sea Anomalybeforeitsnews.com

The Baltic Anomaly is a still-unknown item in the Baltic Sea which some say could be a pre-Ice Age artifact or Nazi anti-submarine device. Oddly, divers’ electrical equipment stops functioning within 650 feet (200m) and a strong radio signal comes off from just near the item.




One of the more commonly referenced deep sea creatures, the anglerfish has an appendage coming out of its forehead with a light on the end. It uses this to lure prey in before devouring them with its over-sized mouth.



NOAA poster

The bloop is another sound picked up by NOAA in the Pacific, but what makes it unique is it was detected at monitoring stations over 3,100 miles (5,000kms) apart. NOAA has now concluded it was ice breaking off a glacier, but some of its scientists still believe it could be a massive marine creature.


Lost Submarines

USS Scorpion launch

The year 1968 saw the still-unexplained loss of submarines by four countries: the United States, Russia, Israel, and France. Some say the losses could have been government cover-ups or (at least in the U.S. case) the nuclear-tipped torpedoes misfiring into the vessel.


Sea Gooseberry

Sea gooseberry

Nicknamed a sea gooseberry, this species of ctenophore has long, sticky tentacles it uses to catch small particles and animals. Unlike most jellyfish, it does not sting.




The aviation industry has experienced numerous unexplained sea disappearances since its founding. Most recently with the Malaysian Airlines MH370 jet, one of the most famous pioneers, Amelia Earhart, also disappeared mysteriously. She and co-pilot Fred Noonan disappeared over the Pacific Ocean in 1937. Millions of dollars have been funneled into finding out the plane’s whereabouts with no success. Rumours include running out of gas and being killed by Japanese troops for spying.


Under(sea)ground Bacteria

Ancient bacteria and fungi

You might think nothing can live beneath the sea floor, but scientists recently discovered bacteria living 1,000 feet (300m) feet below it. Found by drilling through sediment and crust, the bacteria was feeding off residue many millions of years old.


Bigfin Squid

Bigfin Squid

Looking a bit like a boat rudder, the bigfin squid was first seen off the Hawaiian coast in the mid-2000’s and has been scarcely photographed. Including its tentacles, it can reach lengths of up to 16 feet (5m) long.


Battle Snail

Scaly foot snail

Snails aren’t the first animal which come to mind when thinking about body armour, but a newly-discovered (and so yet-named) snail in the Indian Ocean uses iron compounds in the form of scales to protect its fleshy foot. The U.S. military is even researching the snail to improve its battle armour.


Hydrothermal Vent Worms

Riftia tube worm colony

Looking like long lipstick containers, hydrothermal vent worms have neither a mouth nor digestive system. They thus rely on a relationship with bacteria which use chemicals to make food the worms can absorb.


Gonatus Onyx

Gonatus Onyx

Using hooks under its arms, the Gonatus onyx squid holds onto its huge egg mass for many months at a time before they hatch. Talk about a helicopter parent!


Cold Water Corals

Rockfish in red tree coral

Most people think of coral reefs as tropical installations, but we’ve recently discovered there are also cold-water reefs (many of which are being destroyed by trawling vessels). Scientists are in the early stages of study, but they have found a reef off Norway’s coast covering 39 square miles (100 sq kms).


Leptocephalus Giganteus

Sea serpent

Only two of the eel species Leptocephalus giganteus were ever found, and both were larvae. The first (found off the South African coast) was six feet long and, extrapolated to adult size, could measure over 70 feet (21m) long.


Frilled Shark

Frilled shark

Sometimes called a living fossil due to its primitive features, the frilled shark is a rarely-seen animal which may trap its prey by crimping its body and leaping forward like a snake.


Mariana Trench Mystery Shark

Megalodon comparison

While researching marine life at the bottom of the very deep Suruga Bay, Japanese scientists put bait out to attract marine life. Something they weren’t expecting was a shark at least 30 feet (9m) long showing up to the party. Some say it’s the largest Pacific sleeper shark on record (a third larger than the next closest) but some say it’s proof the massive and prehistoric Megalodon still exists.


Underwater Whirlpools

Sully vent

The closest comparison being an underwater tornado, whirlpools exist above some deep sea vents. In certain conditions, they can break away and swirl around like flying saucers, bringing heat, chemicals, and organisms across the ocean. It’s like the wind’s uptake of a dandelion’s spores.


Giant Squid

Giant Squid fight with sperm whale

A massive ocean creature, the giant squid has made a lot of noise in the media but relatively little is known about it. Measuring up to 43 feet (13m) long and weighing up to 1,000 pounds (450kgs), the first live giant squid was filmed in July 2012.


Colossal Squid

Colossal squid on shore

But If you thought it couldn’t get bigger than the giant squid, think again. There’s even less known about the colossal squid which has eyes bigger than your hand. It predominantly lives in the Antarctic and has 25 rotating hooks on the end of each tentacle.


Sulphur Lake

Harvesting sulfur

On the Pacific Ring of Fire lies a lake – a very special lake because it’s both underwater and made entirely of molten sulphur. Thirteen hundred feet (400m) below sea level, the area teems with life including crabs and shrimp specially designed for this bizarre condition.



Stomias boa boa

Firing out a beam of red light from beneath each eye, the bioluminescent dragonfish is the only animal that can see other dragonfishes’ red light. That’s the ultimate in unbreakable secret code.


Macropinna Microstoma


The Macropinna is a fish with a very rare and little understood composition: its head is covered by a transparent, fluid-filled dome. Beyond that, it has barrel-shaped eyes which point up (through the dome) while it’s horizontal in the water and can be rotated forward if it changes position.

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