Meet the Creatures Living in Deep Ocean Trenches

The Cayman Trench plunges 25,216 feet below the Caribbean Sea — deeper than Mount Everest is tall. And at those crushing depths, life doesn’t just hang on; it flourishes in forms that look more like science fiction than biology.

The Cayman Trench, also called the Bartlett Trench, stretches roughly 750 miles along the southern coast of Cuba and the northwestern coast of Jamaica. It’s the deepest point in the entire Caribbean, dropping to 25,216 feet at its lowest spot, the Cayman Abyss. First discovered in 1932 by the ship HMS Challenger during its oceanographic expedition, the trench is a subduction zone where the Caribbean Plate dives beneath the North American Plate — a collision that generates underwater earthquakes and has created active volcanoes like Kick ’em Jenny and Kick ’em Jack below the surface. The trench also hosts the world’s second deepest hydrothermal vents, the Cayman Rise, where “black smokers” spew superheated, mineral-rich water and support unique chemical-dependent life.

In 2025 and 2026, the Beyond the Reef expedition brought 46 scientists together to map and sample across Cayman waters. They mapped more than 4,000 square miles of seafloor, collected nearly 10,000 specimens from surface to depths exceeding 3,600 feet, and used tools including multibeam sonar, environmental DNA sampling, and baited remote underwater video cameras. A CTD device recorded temperature, salinity, and oxygen while collecting water samples — nearly 900 litres processed into 988 samples from depths reaching 1,400 metres. The creatures they captured on camera and in collection nets are the ones you’ll meet here.

Each of these species tells a different story about survival in one of the planet’s most extreme environments. Here’s what the research uncovered.

Ghost Shark (Chimaeras)

Ghost sharks are among the most ancient fish lineages swimming today, and the Cayman Trench is one of the few places in the Caribbean where they appear with any regularity. These chimaeras have soft, scaleless bodies and wing-like pectoral fins that let them glide through the deep water column with almost no effort. They’re not true sharks — they split off from the shark family tree roughly 400 million years ago — and their strange, rabbit-like teeth are built for crushing crustaceans and mollusks.

The Beyond the Reef expedition didn’t capture a ghost shark on camera directly, but local research dives and historical records confirm their presence throughout the trench system. If you’re hoping to see one, you’d need a submersible — these fish rarely venture above 1,000 feet. They’re a reminder that the trench holds lineages that predate the dinosaurs.

Giant Isopod

At 3,116 feet inside a baited camera box, the expedition’s bathysnap system captured something that looked like a pill bug on steroids. The giant isopod — a relative of the common garden pill bug — grew to an estimated 16 inches long and consumed most of the bait before showing any interest in leaving the frame. This is a textbook example of deep-sea gigantism, where species in cold, high-pressure environments grow far larger than their shallow-water relatives.

Giant isopods are scavengers, feeding on dead and decaying animals that drift down from the surface — what scientists call “marine snow.” They can survive months without food, which explains why one was happy to camp out inside the bait box. The species represents a broader pattern in the trench: extreme conditions produce extreme sizes.

Atolla Jellyfish

The Atolla jellyfish is one of the most visually striking residents of the Cayman Trench. It has a burgundy-colored bell and long, swirling tentacles that trail behind it in the dark water. But its most remarkable feature is its bioluminescent defense mechanism. When threatened by a predator, the Atolla jellyfish produces a series of bright flashes — a “burglar alarm” display designed to attract a larger predator that will attack whatever is attacking the jellyfish.

Bioluminescence is a common survival strategy in the trench — many species produce their own light to attract prey, discourage predators, or communicate. The Atolla jellyfish’s version is particularly clever: it doesn’t try to fight or flee; it simply calls in a bigger threat. The expedition’s camera systems captured several Atolla specimens during mid-water trawls, confirming their presence across a range of depths.

Big Red Jellyfish

If the Atolla is the trench’s show-off, the Big Red jellyfish is its ghost. This species can reach up to a meter in diameter — roughly the size of a small coffee table — and its deep red coloration makes it nearly invisible in the dark depths, since red light is the first wavelength absorbed by seawater. The species has been spotted only a handful of times worldwide, and each sighting is a major event for deep-sea biologists.

The Big Red jellyfish’s size and rarity make it a kind of holy grail for deep-sea researchers. The Cayman Trench’s combination of depth, hydrothermal vent activity, and isolated geography may create conditions that allow this species to survive where it can’t elsewhere in the Caribbean. The expedition didn’t confirm a sighting during its 2025-2026 fieldwork, but historical records from earlier submersible dives place it in the trench system.

Glass Sponges

At 1,312 feet on 60-mile Bank, the expedition’s bathysnap camera revealed something that looked more like a cathedral than an animal. Glass sponges — built from silica, the same material as glass — appeared in remarkable abundance, forming complex scaffolds that scientists described as “more architectural than biological.” These fragile structures create habitat for smaller organisms but are easily damaged by fishing gear or physical disturbance.

The expedition’s glass sponge findings are significant because these sponges are indicators of healthy, undisturbed deep-sea environments. They filter water and provide structural complexity that supports everything from tiny crustaceans to juvenile fish. The Beyond the Reef team noted that the abundance of glass sponges at 60-mile Bank suggests the area has experienced minimal human disturbance — a finding that will inform marine protection plans for the Cayman Islands.

Deep-sea Crinoids

At approximately 1,476 feet on an unnamed ridge north of Grand Cayman, the camera lights illuminated a sight that looked more like a coral reef than a deep-sea slope. Deep-sea crinoids — feathery filter-feeders related to starfish — appeared in vivid pink, purple, orange, and yellow, their colors startlingly bright in the otherwise monochromatic deep water. These crinoids perch on elevated spots where currents bring a steady supply of plankton and detritus.

The crinoids’ bright colors are unusual for deep-sea organisms, where most species are white, gray, or transparent. Scientists believe the pigmentation may serve a protective function — possibly warning predators that the crinoids are toxic or unpalatable — or it could be a byproduct of the specific minerals available in the trench’s water chemistry. Either way, they’re one of the most visually arresting discoveries from the expedition’s camera work.

Heading into the unnamed ridge north of Grand Cayman, the crinoid fields reframed what the deep sea looks like. It’s not all gray mud and black water — in the right spot, with the right light, it looks almost like a garden.

Beyond the Six: Other Trench Residents

The expedition recorded several other notable species that didn’t make the top six but are worth knowing about. A deep-sea lobster with claws distinct from spiny lobsters was observed at nearly 2,000 feet on Lawford’s Bank. Earlier in the expedition, an Acanthacaris caeca — a blind clawed lobster — was seen, showing evolutionary adaptation to a lightless environment. Moray eels, typically associated with shallow reefs, appeared at 1,300 feet alongside a conger eel, suggesting that some species are more depth-flexible than previously thought. And at 1,312 feet on 60-mile Bank, a misty grouper over three feet long investigated the baited camera — the first expedition sighting of a grouper that large at that depth. Barophilic bacteria that thrive under immense pressure round out the trench’s microscopic residents.

Protecting the Cayman Trench Ecosystem

For all its depth and isolation, the Cayman Trench isn’t immune to human activity. Plastic waste and microplastics have been documented at trench depths, causing health issues for deep-sea creatures and physically damaging fragile habitats like glass sponge beds. Rising sea temperatures and ocean acidification — driven by global carbon emissions — disrupt the chemical environment that trench species have adapted to over millions of years. Overfishing depletes the “marine snow” of organic matter that drifts down from surface waters, creating a ripple effect that starves deep-sea scavengers and filter-feeders.

The Beyond the Reef expedition’s findings will directly support marine protection, water quality, and fisheries management plans for the Cayman Islands. Some collected specimens have been donated for further study and potential housing at the Cayman Islands Natural Museum. The Department of Environment team also plans a webinar series and district library tour to share findings with the Cayman community — a rare chance for the public to see what lives beneath their coastline.

Before You Go — Deep Ocean Trenches

Can I see any of these creatures on a Cayman Islands trip?

Not directly — these species live at depths exceeding 1,000 feet, far below recreational diving limits. But the Cayman Islands Natural Museum may eventually display specimens from the expedition, and the Department of Environment’s library tour will share footage and findings.

What’s the deepest point in the Cayman Trench?

The Cayman Abyss drops to 25,216 feet (7,686 meters) below sea level, making it the deepest point in the Caribbean Sea. That’s deeper than the Mariana Trench’s shallower sections, though the Mariana Trench overall remains the world’s deepest at roughly 36,000 feet.

Are hydrothermal vents dangerous?

The Cayman Rise vents — the world’s second deepest — emit superheated, mineral-rich water, but they’re so deep that no recreational activity comes near them. They’re safe to study remotely and provide a unique chemical environment that supports life forms not found anywhere else in the Caribbean.

What’s the biggest threat to trench ecosystems?

Plastic pollution and microplastics have been documented at trench depths globally, and the Cayman Trench is no exception. Combined with rising ocean temperatures and overfishing that depletes the food web, human impact reaches even the most remote deep-sea environments.

How do deep-sea creatures survive the pressure?

Many trench species have flexible, gelatinous bodies without rigid bones, plus anti-freeze proteins and slower metabolic rates. Some, like the blind clawed lobster Acanthacaris caeca, have lost features they don’t need — like eyes — in favor of adaptations that help them thrive in crushing darkness.

Closing

The Cayman Trench is easy to forget about when you’re floating in turquoise water or relaxing on Seven Mile Beach, but it’s the hidden foundation of the entire island ecosystem. The same geologic forces that created the trench also built the islands above it, and the creatures that live down there — from giant isopods to architectural glass sponges — are part of the same story. Next time you look out at the water, you’ll know there’s a whole other world beneath it.

For more on the marine life you can actually swim with, check out our guide to encountering Cayman’s amazing marine life — from stingrays to reef sharks and everything in between.

References

Cayman Compass. “Creatures of the deep: Cayman’s hidden ocean revealed.” 21 March 2026. ↗

Snorkel.ky. “Mysterious Marine Life: Cayman Trench.” ↗

If you’re planning a trip centered on marine life, our guide to diving with sharks and exploring beyond the reef covers the shallower side of Cayman’s underwater world. For something completely different, the bioluminescent bay kayak tour offers a nighttime glimpse of the ocean’s glow — a surface-level echo of the trench’s own light shows. And if remote cays are more your speed, our guide to Cayman’s remote cays takes you to the quiet edges where the deep sea meets the shore.