Under the waterline lies a vast world of mystery and wonder, home to some of the most beguiling creatures on Earth. Marine life can be shocking, that’s for sure, and at times incredibly dangerous, but it never fails to be astounding.
In this list, we will be delving into the underwater world, from the shallows of the river banks to the depths of the ocean, to uncover some of the most astonishing stories of underwater life. Prepare yourselves for drugged-up guppies, hot-headed orcas, and a lobster that looks like cotton candy, among many other peculiar sea-dwellers.
But perhaps the most remarkable thing about underwater life is just how much is out there still waiting to be discovered. Who knows what wonders could be lurking beneath the waves?
Related: 10 Amazing Animals with Unique Environmental Adaptations
10 The Immortal Freshwater Hydra and its Contagious Cancer
The Hydra oligactis is a fascinating and perplexing being. The jellyfish-like creatures are said to be “immortal” due to the strange way they reproduce. A parent hydra will create tiny buds that grow into clones. They’re also one of the few known animals that can transmit cancer. Hydras pass their tumors onto their identical offspring.
Ecologists decided to delve into this strange spectacle. Hydras are known to form tumors when they overeat. So researchers from the French National Centre for Scientific Research gorged the creatures on lavish amounts of brine shrimp larvae.
After two months, nineteen of the overfed hydras were swelling with tumors. The team then collected their young and repeated the process over several generations. They discovered that hydras from tumorous parents were four times more likely to develop tumors of their own than those whose parents did not have growths. This was unusual, given that all the creatures were genetically identical. Scientists hope that further research will provide a new insight into cancer development, as well as human impact on ecosystems.[1]
9 Young Jackfish Wears Jellyfish as Armor
In 2024, ocean photographer Katherine Lu unveiled her photograph showing the unlikely relationship between a young jackfish and a jellyfish. The scaled critter hides inside the gelatinous animal for protection. Jellyfish do, of course, sting. But as Lu explains, the fish build an immunity to the toxin. “The jellyfish then provides a safe haven for the fish against larger ocean predators while the jellyfish is pushed through the water column by the fish, increasing its ability to feed.”
Lu’s remarkable picture was showcased as part of the Ocean Photographer of the Year awards. Other featured images from the deep include a shoal of ghoulish plainfin midshipman fish. The baby swimmers have bulging black eyes. In the photo, they are still tethered to their yolk sacks.
Among the other spellbinding snaps were opalescent squids and Western toad tadpoles, which Shane Goss photographed from underneath while snorkeling. But the overall award for Ocean Photographer of the Year went to Rafael Fernández Caballer, who captured the rare image of a Bryde’s whale ready to feast on a ball of bait.[2]
8 Cold Water Fends Off Bass Invasion at Grand Canyon
The Grand Canyon is in danger of being overrun with predatory fish. Invasive smallmouth bass are a menace to native species like the humpback chub living in the Colorado River. The smallmouth fish usually live in the eastern and central United States. But when scientists discovered them breeding downstream of the Glen Canyon Dam, they feared the predators could threaten the Canyon’s ecosystem.
The U.S. Bureau of Reclamation knew they had to act to protect the chub and other native fish. So the decision was made to lower the temperature of the Colorado River. Officials released water from Lake Powell, making the river too cold for the smallmouth bass to reproduce.
Their plan went into action in July 2024. At the time of writing, it seems to be a success. So far, experts have found no signs of any newly hatched bass. It seems as though officials have limited the bass’s potential damage without the need to release harmful, fish-killing chemicals into the river.[3]
7 A Surge in Orcas Attacking Boats around the Iberian Peninsula
Orcas around the Iberian Peninsula keep attacking boats, sometimes causing so much damage that the sailors are left stranded. The marine menaces are becoming increasingly violent, with over 600 attacks reported between 2020 and 2024. Smaller boats off the coast of Spain, Portugal, and Morocco are most at risk of orca assault. Sailors say the killer whales like to target the rudders.
Until recently, scientists have been at a loss to explain this surge in orca aggression. But in August 2024, the Bottlenose Dolphin Research Institution in Spain suggested that the whales could be in training. Orcas hunt some pretty ferocious prey, such as the Atlantic bluefin tuna. Researchers believe the black and white beasts are going after small boats to prepare to take down large, speedy fish.
“During interactions with vessels, killer whales have been documented engaging in diverse actions, such as strokes, corporal lever movement, and biting of varying intensity,” the dolphin experts explained. “These behaviors could potentially serve as an exercise for killer whales, where vessels act as stimuli for play, fostering cooperative techniques, preparing for pursuits of [Atlantic bluefin tuna], and facilitating improvements in motor skills, ultimately simulating hunting techniques.”[4]
6 “Shazam for Whales” Identifies Moaning from Mariana Trench
Since 2014, scientists have been scratching their heads as to the origin of a strange moaning noise coming from the Mariana Trench. But the elusive howling can now be attributed to Bryde’s whales, thanks to AI.
The specialized algorithm, described as “Shazam for whales,” was developed by the National Oceanic and Atmospheric Administration, working with a team of Google developers. The researchers already had thousands of hours of underwater recordings from hydrophones on the Pacific sea bed. Google trained its AI to pick up the call patterns of specific whales within the sound clips.
Together, they identified that the strange moaning was caused by Bryde’s whales from the nearby Mariana Islands. And that’s not all. AI analysis of the call patterns is helping scientists track the whales’ behavior. Evidence suggests that the enormous creatures are following a boundary of hot and cold water that is rich in plankton and other prey.[5]
5 All-Female Shark Slumber Party in Australia
It’s ladies’ night every night on the seabed of the Beagle Marine Park in the Bass Strait of Australia. Venture into the depths, and you will find thousands of female Port Jackson sharks dozing on the seafloor. Scientists first came across the marine slumber party using a remotely operated vehicle in 2018. Six years later, they returned to survey how conditions have changed.
Port Jackson sharks have a distinctive look: blunt heads and markings on their bodies that make it look like they’re wearing harnesses. The males and females live separately for most of the year, only coming together to mate.
Scientists believe the female predators could be resting to prepare to lay their eggs. As marine researcher Dr. Jacquomo Monk explained, “We don’t know exactly why the females are here. Perhaps they are feasting on the local delicacy—doughboy scallops—before the long trip north to lay their eggs.”
Port Jackson sharks have been known to swim as far as 373–497 miles (600–800 kilometers) between the breeding and laying sites. The fact that they are still using the site six years later suggests that Beagle Marine Park is a key pillar on that long voyage to produce new life.[6]
4 Scientists Discover New Species of Miserable Fish, Grumpy Dwarfgoby
Life underwater isn’t always fun and games. But one fish who feels the drudge more than most is the grumpy dwarfgoby. The goby is one of the marine world’s most miserable inhabitants. Scientists discovered the moody fish moping around the Red Sea near Saudi Arabia. The dismal creature got its name due to its “apparent grumpy and rather unhappy appearance, primarily due to the extremely upturned mouth position.” Researchers announced their discovery in a 2024 paper in ZooKeys.
Although only around the size of a grape, the goby has been described as a minuscule menace. Beneath its frown is a set of ferocious canines that the unhappy predator uses to snap up its prey. Despite its unusual appearance, the goby is a reminder of how much undiscovered life exists beneath the ocean blue.[7]
3 Drug Residue in Waterways Wreaking Havoc with Fish
Pharmaceutical pollution is a rising issue in our waterways, and experts warn it could harm the survival of some species. Chemical residue in rivers and streams can throw aquatic life into disarray. Fluoxetine—an antidepressant often sold as Prozac—has been seen disrupting the growth of guppies in Australia. Even in low doses, scientists show that the drug causes a drop in sperm count among males. This isn’t just bad news for the guppies; it threatens the ecosystem as a whole.
These contaminants enter the waterways through wastewater. Sewage treatment plants often fail to remove chemical residue. Plenty of drugs still linger in the water and are released into the environment. Scientists say we need to find ways to stop drugs like Prozac from harming sensitive ecosystems.[8]
2 Cuttlefish Can Create False Memories Just Like Humans
Fish are often said to have terrible memories. But it looks like some of our aquatic pals recall events in a way closer to humans than we thought. Scientists have found evidence to suggest that cuttlefish are susceptible to false memories. The creatures sometimes become jumbled when thinking back on a past event, so the experts believe.
The marine mollusks are remarkable creatures with fantastic recall skills. Researchers at the University of Rouen Normandy wanted to dive deeper into how cuttlefish memory works. They devised an experiment using containers of crab meat and shrimp to find out if the mollusks remember things all at once or if they reconstruct fragments of memories like humans.
The team found evidence of cuttlefish drawing on false memories in their snack-based trial. It appears that our brainy mollusk buddies remember things in segments and are more similar to human intelligence than we previously realized.[9]
1 Fisherman Discovers Ultra Rare Cotton Candy Lobster
In July 2024, Joseph Kramer was taken aback by what he uncovered in a lobster trap in the waters of New Hampshire. The fisherman expected to haul up regular crustaceans. But instead, he was greeted by a glistening “cotton candy” lobster, its carapace a dazzle of blues, purples, and pinks.
The wondrous creature is now on display at the Seacoast Science Center in Rye, where visitors can take in its exceptional coloring. Sam Rutka, an aquarist at the center, explained that the catch has a rare genetic condition found in one in every 100 million lobsters. Although beautiful to look at, the colored carapace doesn’t help all that much in the wild. The colorful crustaceans find it much more difficult to camouflage than their regular cousins. Experts say it makes it all the more remarkable that this splendid animal avoided predators for so long before being scooped up in one of Kramer’s traps.[10]