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The Living Ocean

A barreleye fish can look up through its own transparent head. Thirty-three photographs of what lives in the ocean, from Mediterranean seagrass to animals filmed more than two miles down.

33 photographs / Tap a photo to enlarge

A living barreleye fish with green tubular eyes inside its transparent head.
Barreleye · Macropinna microstomaThe green spheres inside its head are its eyes. They look upward through a transparent dome, then rotate forward when the fish feeds. The two dark spots above its mouth are smell organs.ResearchPhoto: MBARI

Sunlit water

A silvery school of fish hovering over a green seagrass meadow in clear blue water.
Neptune grass · Posidonia oceanicaThis meadow is near Marseille, France. Seagrass spreads by growing new shoots from underground stems. The leaves come and go, but some Mediterranean clones have persisted for thousands of years.ResearchPhoto: Karim saari
Purple ochre sea stars crowded together on a wet rock face.
Ochre sea stars · Pisaster ochraceusRobert Paine removed these sea stars from a stretch of Washington shore. Mussels took over, crowding out other species. The experiment helped establish the idea of a keystone species: an animal with an effect far larger than its numbers suggest.ResearchPhoto: Collin Smith / USGS
A lined chiton with eight pink and green patterned shell plates on a rock.
Lined chiton · Tonicella lineataChitons scrape food off rocks with a ribbon of teeth called a radula. The working tooth tips are hardened with magnetite, an iron oxide. They grow replacements as the old teeth wear down.ResearchPhoto: Jerry Kirkhart
A sunlit coral outcrop of staghorn, plate and boulder corals with small fish hovering above in blue water.
Great Barrier Reef · Flynn Reef, Australia · More than 2,900 reefsThe Great Barrier Reef contains more than 2,900 separate reefs. Each coral colony is made of small animals called polyps, which build the limestone skeleton beneath them. The branching and plate-shaped colonies here share one outcrop.ResearchPhoto: Toby Hudson
A mandarinfish with blue and orange maze-like markings sheltering beside coral.
Mandarinfish · Synchiropus splendidusMany blue fish get their color from microscopic structures that reflect light. Mandarinfish also have cells containing blue pigment, called cyanophores. Researchers found them in this fish and its close relative, the psychedelic mandarinfish.ResearchPhoto: Diego Delso
A cobalt-blue eel with flared yellow nostril flaps curling out of a reef.
Ribbon eel · Rhinomuraena quaesitaThe yellow flaps on its snout are expanded nostrils. Young ribbon eels are black with a yellow dorsal fin; adult males are blue and yellow. They usually live in burrows in sand or rubble beside coral reefs.ResearchPhoto: Rickard Zerpe
A banded brown-and-white octopus with long arms fanned out over dark volcanic sand.
Mimic octopus · Thaumoctopus mimicusIt can flatten itself into the shape of a flatfish or trail two banded arms like a sea snake. Researchers saw it use the snake-like display when harassed by damselfish. The disguise changes with the situation.ResearchPhoto: Rickard Zerpe
A small octopus with translucent veined webbing perched on a shell against dark sand.
Coconut octopus · Amphioctopus marginatusResearchers filmed these octopuses carrying coconut-shell halves across the seabed, then assembling them into shelters. Carrying the shells makes walking awkward. The payoff comes later, when the octopus needs somewhere to hide.ResearchPhoto: Rickard Zerpe
A small ochre octopus covered in glowing electric-blue rings on dark ground.
Blue-ringed octopus · Hapalochlaena sp.Its bite can deliver tetrodotoxin, which blocks nerve signals and can paralyze breathing muscles. The blue markings become conspicuous when it's disturbed.ResearchPhoto: Shaymary
A peacock mantis shrimp with red limbs, green shell plates and blue markings on the seabed.
Peacock mantis shrimp · Odontodactylus scyllarusIts strike produces two impacts: the club hits, then a vapor bubble collapses against the target. The bubble forms because the fast-moving club drops the water pressure, a process called cavitation. Both impacts help break a shell.ResearchPhoto: Cédric Péneau
A dark sea slug with green stripes and orange markings crawling over the reef.
Variable neon slug · Nembrotha kubaryanaThis sea slug eats sea squirts. Chemists isolated a blue pigment from its body that had already been found in sea squirts, suggesting it came from the slug's food.ResearchPhoto: Diego Delso
A small white crab covered in red polka dots sitting on a folded carpet anemone.
Porcelain crab · Neopetrolisthes maculatusThe anemone provides shelter among its stinging tentacles. The crab feeds by sweeping feathery mouthparts through the water and collecting suspended food. The large claws are separate from these feeding fans.ResearchPhoto: Diego Delso

In open water

A purple Portuguese man o' war stranded on a tropical beach.
Portuguese man o' war · Physalia physalisA man o' war is a colony of connected, genetically identical parts called zooids. They specialize in feeding, catching prey, and reproduction. The gas-filled float carries the colony along with the wind and current.ResearchPhoto: Andrespuche
Several blue sea slugs with branching appendages lying on a pale surface.
Blue dragons · Glaucus spp.These slugs drift at the surface and feed on bluebottles and other floating stinging animals. They store some of their prey's stinging capsules at the tips of their finger-like branches, where the capsules can still fire.ResearchPhoto: Doug Beckers
A leopard seal looking toward the camera at the surface in gray water.
Leopard seal · Hydrurga leptonyxPhotographer Paul Nicklen describes a leopard seal bringing him live penguins, then dead ones, during an Antarctic assignment. He interpreted it as an attempt to feed him. What the seal intended is harder to establish.ResearchPhoto: Gilad Rom
Two sperm whales swimming horizontally just below the blue ocean surface.
Sperm whales · Physeter macrocephalusThese two are swimming, but sperm whales also rest upright just below the surface. Researchers recorded whales drifting almost motionless and failing to react to a passing boat, suggesting they were asleep. Those dives occupied about 7% of the study's recording time.ResearchPhoto: Gabriel Barathieu
A giant manta ray seen head-on with its mouth open and head fins curved outward.
Giant manta ray · Mobula birostrisTwo captive mantas made unusual repeated movements in front of a mirror, including exposing parts of their bodies to it. Researchers suggested they might be inspecting themselves. That small study didn't establish that mantas pass the standard mirror self-recognition test.ResearchPhoto: Arturo de Frias Marques
A great white shark approaching a bait line at the sea surface.
Great white shark · Carcharodon carchariasA tagged white shark named Nicole traveled from South Africa to Australia, about 6,900 miles in 99 days. She was identified back at the original South African tagging site less than nine months after departure. The outward trip was tracked; the return was confirmed by her markings.ResearchPhoto: Andrew Shiva
A green sea turtle swimming above a pale sandy seabed.
Green sea turtle · Chelonia mydasGreen turtles nesting on Ascension Island feed along the Brazilian coast, more than 1,400 miles away. Satellite tags have followed females across that stretch of open Atlantic, often along remarkably straight routes.ResearchPhoto: Charles J. Sharp

Under the microscope

A spherical radiolarian skeleton with a fine mesh surface and two long opposing spines.
Radiolarian · Stylosphaera coronata laevisThis perforated skeleton belonged to a single cell. Many radiolarians build their skeletons from silica, the main ingredient in glass. Their remains settle to the seafloor and become part of the sediment.ResearchPhoto: Picturepest
A chain of transparent diatom cells with golden-brown contents under a microscope.
Diatoms · Light micrograph · About 20% of global carbon fixationDiatoms are estimated to carry out about a fifth of the planet's photosynthetic carbon fixation, turning carbon dioxide into organic matter using sunlight. Each cell in this chain does that work inside a silica shell.ResearchPhoto: John R. Dolan, NOAA
A round diatom shell with rings of closely packed pores under a microscope.
Diatom shell · Stephanopyxis grunowiiA single-celled alga made this patterned silica wall. In other diatom species, researchers have measured how regular pore arrangements guide and filter light, much like manufactured photonic materials.ResearchPhoto: Anatoly Mikhaltsov

Below the sunlight

Submersible lamps reveal the colors in these deep-sea photographs. The water around the animals is dark.

A vertical siphonophore colony with transparent swimming bells and orange feeding structures.
Siphonophore · Marrus orthocannaThe transparent bells propel a colony of connected zooids, each specialized for a job. Feeding structures trail below them. The colony grows by budding new parts from one fertilized egg.ResearchPhoto: Kevin Raskoff, Monterey Peninsula College
A giant phantom jelly with a dark red bell and broad ribbon-like arms in deep water.
Giant phantom jelly · Stygiomedusa giganteaIts bell can grow more than three feet across, and its four mouth-arms can exceed 33 feet. MBARI has filmed small fish swimming among those arms. Open water offers few hiding places; a jelly can provide one.ResearchPhoto: MBARI
A dark mineral plume rises from a hydrothermal chimney above a dense bed of tubeworms.
Sully hydrothermal vent · Northeast PacificThe dark plume carries mineral particles, not smoke from a fire. Around vents, microbes use energy from chemical reactions to make food, a process called chemosynthesis. They support animal communities where sunlight can't reach.ResearchPhoto: NOAA
A close-up of a Pompeii worm with red gill filaments and bristled appendages.
Pompeii worm · Alvinella pompejanaIt lives in tubes on hydrothermal chimneys, where hot vent fluid meets cold seawater. In a pressurized aquarium, most survived a heat test that reached 108 F. Two hours at 122 to 131 F killed them.ResearchPhoto: Olivier Dugornay

Recently described

A transparent swimming sea slug with a broad hood, fingered tail, and visible reddish internal organs.
Described 2024Mystery mollusc · Bathydevius caudactylusMBARI researchers first saw this swimming sea slug in 2000 and described it in 2024. Its broad hood traps small crustaceans. It can also release a glowing finger from its tail, apparently as a decoy, then grow a replacement.ResearchPhoto: MBARI
Two red-and-white female tailspot wrasses with black patches swimming beside volcanic rocks.
Described 2024Tailspot wrasse · Halichoeres sancheziA diver photographed an unfamiliar wrasse in 2013. Researchers collected it near San Benedicto Island, Mexico, during a 2022 survey and confirmed it as a new species. These are two females; the larger males have a different color pattern.ResearchPhoto: Allison and Carlos Estape
A rose-veiled fairy wrasse with a pink head and blue-edged fins swimming beside a reef.
Described 2022Rose-veiled fairy wrasse · Cirrhilabrus finifenmaaScientists had mistaken this Maldivian fish for an adult of another species. Ahmed Najeeb helped describe it as a separate species, the first fish formally described by a Maldivian researcher. Finifenmaa means rose in Dhivehi.ResearchPhoto: Luiz A. Rocha
A translucent comb jelly hovering above the seabed with two long tentacles trailing behind.
Described 2020Duobrachium comb jelly · Duobrachium sparksaeNOAA scientists described this comb jelly from video alone, without collecting a specimen. Three sightings came from one dive near Puerto Rico, about 2.4 miles down. Its tentacles appeared to touch the seabed while its body hovered above.ResearchPhoto: NOAA Ocean Exploration
A pale glass sponge with two large openings on a long stalk beside a sampling arm.
Described 2020E.T. sponge · Advhena magnificaThe holes that look like eyes are openings in a glass sponge. Water moving through its body brings food particles. Its shape suggested the name Advhena magnifica, magnificent alien; anatomical study established the new genus.ResearchPhoto: NOAA Ocean Exploration
A yellow-and-magenta Aphrodite anthias sheltering beneath a reef ledge.
Described 2018Aphrodite anthias · Tosanoides aphroditeDivers collected this fish about 390 feet down at St. Paul's Rocks in the Atlantic. Genetic analysis placed it in a genus previously known only from the Pacific. The species name honors Aphrodite, the Greek goddess of beauty.ResearchPhoto: Luiz A. Rocha

Photographs and sources

Research and photo sources are linked beneath each image. Photographs are reproduced at their original proportions. The credits below record the source and its stated rights.