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Meet the creatures of the deep, dark sea

In the darkness of the open water, rarely seen creatures dance along the ocean current.

A juvenile African pompano, or threadfin trevally, swims through the Verde Island Passage, a major shipping lane in the Philippines. Its streaming filaments resemble the tentacles of a jellyfish—a possible advantage for evading predators that patrol the night sea.
ByAmy McKeever
Photographs byJennifer Hayes and David Doubilet
September 09, 2021
8 min read

In the open ocean in the dead of night, a light-studded downline silently sinks a hundred feet into the water’s inky depths.

The National Geographic Society, committed to illuminating and protecting the wonder of our world, has funded Explorer David Doubilet since 2012. This is the 50th anniversary of his first assignment as a National Geographic photographer. Doubilet and Jennifer Hayes document both the beauty and the devastation in our oceans.

Minutes later, there’s a splash as divers plunge in too. Equipped with scuba gear, a bevy of lights, and waterproof DSLR cameras clipped to their suits, National Geographic's David Doubilet and Jennifer Hayes descend into a realm of the unimaginable.

“When you first get in, it is a galaxy of light,” Doubilet says of black-water diving. “You see fellow divers with their shafts of focusing lights and red lights: a galaxy here and a galaxy there.”

In the dark—whether it’s the Sargasso Sea of the North Atlantic or the tropical waters off Indonesia’s Raja Ampat archipelago—Doubilet and Hayes see things even many other marine biologists (Hayes is one) will never see. Black-water diving is “the equivalent of a marine ‘Sorcerer’s Apprentice,’” Doubilet says. “All strange things that are dancing around at night.”

When night falls on the open sea, there’s a world to explore as zooplankton swim up from the depths to feed. Many of these small organisms are still larvae, including the mantis shrimp pictured here. Mantis shrimp are voracious predators in their larval and adult phases, and black-water diving offers a rare glimpse into their early lives. “It’s the nursery of the ocean,” says Doubilet.

The duo capture rare images of creatures in their larval forms and observe the clever ways the animals survive the night, like a juvenile jack that hides behind a jellyfish. But as the current propels them through the sea, divers must keep an eye on their bubbles to remember which way is up—and on the downline’s lights to make sure they don’t drift too far from their boat.

“It’s all at the mercy of the current,” Hayes says. “You’re just moving with [the animals], lucky to encounter them.”

To travel safely through the night, this larval carangid hops a ride on the back of a moon jelly. Safety is also on the minds of humans, who are at the mercy of the current. Divers drop a rope studded with bright lights into the sea, attached to a buoy at the surface. Both divers and their boat orient toward the light to ensure no one gets lost.
Zooplankton—such as a jellyfish (1) and a larval lionfish surrounded by tiny, shrimplike amphipods (2)—often swim from the deep toward the surface at night to feed. Diving in the open ocean after sundown is “a grandstand seat to a parade of the most strange and exotic creatures in the world,” Doubilet says.
Some sightings are rarer than others, such as this immortal jellyfish that Hayes photographed in Anilao, Philippines. When threatened, this glowing bell-shaped invertebrate can revert to its earliest life phase—essentially restarting its life. It’s one of several animals considered to be the holy grail for black-water divers. For Doubilet and Hayes, the elusive blanket octopus tops the list.
The mirror image of a brilliantly colored flying fish is reflected on the underside of the sea’s surface off Bermuda. Topside, these fish can glide up to 650 feet across the water by stretching out their pectoral fins like wings.
A pelagic squid releases a cloud of ink before vanishing into the depths of Indonesian waters. The night sea can be mesmerizing, Doubilet says, but it can be frustrating to photograph because many animals are tiny and skittish: “As you move the focus, the creature spins this way or that, and you might not get it.”
This sea butterfly is a free-swimming snail that can be as small as a grain of sand whose foot has evolved into wing-like lobes that flap to propel it through the water.
Picture of a juvenile cowfish.
Hayes photographed a coin-size juvenile cowfish off Indonesia’s coast. Doubilet likens this style of night diving—being carried by the currents—to drifting through space. “The only way to know which is up is to watch which direction the bubbles are going,” he says.
Some animals attempt to camouflage themselves for protection—such as this pipefish, which is pretending to be the stick it’s carrying through the night sea in Anilao, Philippines. Blackwater divers worry about predators, too—especially sharks. But sadly, Doubilet says, sharks have been fished out of most of the places where they dive. “You feel relatively safe for all the wrong reasons.”
This juvenile trevally has hidden itself inside a jellyfish to escape the notice of predators near Moalboal, Philippines.
Originally identified as radiolaria—single-celled plankton with a hard mineral shell—this photograph more likely depicts an egg mass spawned by an unidentified species. Many night sea encounters are not immediately identifiable; photographs are circulated within an active community of scientists and divers who work together to learn about this unique ecosystem.
An amphipod hitchhiker sits atop a jellyfish.
Picture of a juvenile jack fish hiding behind a jellyfish as it swims.
A juvenile jack hides behind a jellyfish—driving it like a motorboat. As the jellyfish provides protection from predators, the juvenile fish may feed on parasites that have latched onto its host. “You rarely run into something that doesn’t fascinate you,” Hayes says. “It really is a new macroscopic lens into the sea.”

The National Geographic Society is committed to illuminating and protecting the wonder of our world. Learn more about the Society’s support of its ocean Explorers.

This story appears in the October 2021 issue of National Geographic magazine.

This story originally published digitally on July 9, 2020, and has since been updated with more detailed text and captions.

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