Meet the creatures of the night sea

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.”

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.”

Zooplankton—such as a jellyfish (left) and a larval lionfish surrounded by tiny, shrimplike amphipods (right)—often swim from the deep toward the surface at night to feed. Diving in the open ocean after sun- down 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.

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.

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.

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.

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.”

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.

This juvenile trevally has hidden itself inside a jellyfish to escape the notice of predators near Moalboal, Philippines.

An amphipod hitchhiker sits atop a jellyfish.

Zooplankton—such as a jellyfish (left) and a larval lionfish surrounded by tiny, shrimplike amphipods (right)—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.

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.