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Photographer Captures Ocean's Hidden Nightlife
When Jialing Cai descended into the ocean's inky blackness at night, she discovered a world teeming with life few have witnessed. The Chinese photographer, specializing in blackwater diving, has spent years documenting the mesmerizing creatures that rise from the deep during the planet's largest animal migration.
The Art of Blackwater Diving
Blackwater diving involves floating in open water at night, where the ocean floor vanishes into an abyss. Cai describes the experience as disorienting-without visual references, divers risk drifting into dangerous depths. Yet, the thrill of encountering deep-sea creatures up close outweighs the fear.
"There is no reference for you to know your location in this three-dimensional space," Cai explains. "But the excitement overwhelmed my fear." What appears as an empty void is, in fact, a bustling ecosystem of juvenile fish, octopuses, jellyfish, and microscopic copepods.
Award-Winning Glimpses of the Deep
Cai's work has earned global recognition. In 2023, she was named Oceanographic magazine's Ocean Photographer of the Year for her image of a paper nautilus, a rare octopus with a delicate, shell-like egg case. By 2025, she secured the Oceanographic Female Fifty Fathoms Award for her collection showcasing the ocean's most elusive inhabitants.
Her technique doesn't require deep dives. Instead, she waits for creatures to ascend from the depths at night-a phenomenon known as diel vertical migration (DVM). "I realized I could take glimpses into a world my mortal body would never allow me to reach," she says.
The Science Behind the Migration
Every night, trillions of zooplankton rise from the ocean's twilight zone to feed near the surface, creating the largest biomass migration on Earth. This daily ritual, occurring in every marine environment, sustains ecosystems by providing food for fish, whales, and other predators.
Jon Copley, a professor of ocean exploration at the University of Southampton, emphasizes the importance of Cai's work. "Photographic evidence of these animals is crucial because they're rarely seen in their natural habitat," he says. Traditional net collections often damage specimens, obscuring their true forms.
Chasing the Invisible
Cai's first blackwater dive in the Philippines in 2018 nearly ended in disaster. Hyper-focused on photographing a wunderpus octopus, she drifted too far from her dive boat. "I turned off all my lights, hoping to spot the boat's glow," she recalls. "There was nothing but blackness." After surfacing, the crew finally located her-a moment she describes as feeling like a lifetime.
Her images reveal behaviors rarely observed. A juvenile trevally fish, for instance, uses a jellyfish's venomous tentacles as a shield. Another shot captures a tiny crab mid-molt, shedding its exoskeleton like a sweater.
Threats to the Twilight Zone
The mesopelagic zone, stretching from 200 to 1,000 meters below the surface, hosts the majority of marine life. Yet human activity-overfishing, climate change, and pollution-threatens this critical ecosystem. Research predicts a 40% decline in twilight zone life by century's end due to warming oceans.
Copley warns that protecting this zone is urgent. "Climate change will curtail life here dramatically," he says. Cai's photographs serve as a reminder of the ocean's fragile beauty and the need for conservation.
Everyday Encounters with Deep-Sea Travelers
Many coastal creatures begin life as plankton, drifting vast distances before settling. A common shore crab, for example, may have journeyed hundreds of miles in its larval stage. "Next time you see one in a seaside bucket," Cai says, "remember-it survived against all odds."
"These tiny critters form the basis of the food chain. They're vital for everything from fish to whales."
Laura Hobbs, Arctic marine scientist
