What Are the 5 Layers of the Ocean? A Deep Dive

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Zoologist and wildlife educator Cassandra Ray explains the major open-ocean zones

Co-authored by Cassandra Ray and Samantha Fulton, BA

Last Updated: August 24, 2026 Fact Checked

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• Epipelagic Zone (Sunlight Zone)
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• Mesopelagic Zone (Twilight Zone)
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• Bathypelagic Zone (Midnight Zone)
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• Abyssopelagic Zone (Abyssal Zone)
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• Hadalpelagic Zone (Hadal Zone)
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• Video
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• Tips

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If you’re interested in learning more about the ocean and its distinct zones, you’ve come to the right place. The ocean is a vastly unexplored ecosystem that’s filled with fascinating creatures and is vital for our environment. We talked to a zoologist and wildlife educator to give you the rundown on each of the layers of the ocean and the unique organisms that live in each one (complete with links to videos of the coolest animals). Plus, we’ll give you easy ways to contribute to ocean conservation efforts along the way. Let’s dive in!

What are the 5 zones of the ocean?

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Zoologist and wildlife educator Cassandra Ray says that the open-ocean zones are:

• Epipelagic (Sunlight) Zone: The uppermost zone, where photosynthesis occurs. Depth: Extends 200 m (656 ft) from the surface.
• Mesopelagic (Twilight) zone: Contains billions of organisms that help control our climate. Depth: Extends from 200 to 1,000 m (656 to 3,280 ft) deep.
• Bathypelagic (Midnight) zone: Accounts for 70% of seawater and is the largest habitat on Earth. Depth: Extends from 1,000 to 4,000 m (3,280 to 13,123 ft) deep.
• Abyssopelagic (Abyssal) zone: Makes up the planet’s seafloor. Depth: Extends from 4,000 to 6,000 m (13,123 to 21,325 ft) deep.
• Hadalpelagic (Hadal) zone: Refers to deep oceanic trenches with rare and unique organisms. Depth: Extends from 6,000 to 11,000 m (19,685 to 36,089 ft) deep.

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1

Epipelagic Zone (Sunlight Zone)

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1. 
   The epipelagic zone is the uppermost 2 to 3 percent of the ocean. Ray says, “This is the part of the ocean that receives enough sunlight for photosynthesis. Phytoplankton live here and form the foundation of many marine food webs, which means this zone supports an enormous amount of ocean life.” In fact, the epipelagic zone produces 50% of the world’s oxygen—phytoplankton use photosynthesis to generate oxygen, while simultaneously absorbing carbon dioxide (which fights climate change)!

   • How deep is it? This zone extends from the surface down to 200 meters (656 feet).
   • What are the temperatures? Temps can range from 28 to 97°F (-2 to 36°C).
   • What lives there? This zone contains 90% of all marine life! Ray says that this zone includes dolphins, sea turtles, tuna, sharks, manta rays, jellyfish, and schools of fish. She adds that it’s also the home of “coral reefs and many other highly productive coastal ecosystems.”
     • Meet a sunlight zone native! Dolphins are social and highly intelligent creatures who call the sunlight zone home. Check out this video to see a mama dolphin teaching her calf a sick trick.
   • Dive into ocean conservation: Conserve water around your home by taking shorter showers and not leaving sinks running. This prevents excess runoff and wastewater from flowing into the ocean.

   Meet the wikiHow Expert

   Cassandra Ray is a zoologist, wildlife educator, and conservation communicator who has worked in wildlife education, conservation outreach, and field research around the world.
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2

Mesopelagic Zone (Twilight Zone)

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   The mesopelagic zone makes up 20% of the ocean’s volume. “This is where things start getting really strange,” says Ray. “Only a tiny amount of sunlight reaches this zone, and there isn’t enough light for photosynthesis. Many animals have evolved incredible adaptations for seeing, hiding, and hunting in near-darkness.” This zone is also important for regulating the ecosystem, she adds. “Huge numbers of animals migrate toward the surface at night to feed, then return to deeper water during the day. This daily movement helps transport carbon and nutrients through the ocean.”

   • How deep is it? The twilight zone extends from 200 to 1,000 meters (656 to 3,280 feet) deep.
   • What are the temperatures? Temps decline with depth, getting down to about 40°F (5°C)
   • What lives there? “Some of the coolest residents include lanternfish, hatchetfish, dragonfish, squid, krill, jellies, and bioluminescent organisms,” explains Ray.
     • Meet a twilight zone native! The strawberry squid has mismatched eyes that help it hunt food in the dark of the twilight zone. Check out this video to see one up close.
   • Dive into ocean conservation: Reduce your use of single-use plastics (like straws and water bottles) to curb plastic pollution. This can help protect sea creatures from consuming plastic.

3

Bathypelagic Zone (Midnight Zone)

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1. 
   The bathypelagic zone accounts for 70% of all seawater. “At this point, sunlight is completely gone,” says Ray. “The water is cold, pressure is enormous, and food becomes much harder to come by.” She says that many animals in this zone rely on marine snow, a.k.a. “tiny pieces of dead organisms and organic material slowly sinking down from the upper ocean.” She adds that many animals here use bioluminescence, including glowing organs that act like flashlights or lures, or lights that camouflage the animal from predators looking upwards.

   • How deep is it? This zone extends from 1,000 to 4,000 meters (3,280 to 13,123 feet) deep.
   • What are the temperatures? The midnight zone has a steady temperature of around 39°F (4°C).
   • What lives there? Ray says, “This is where you start encountering some of the animals people traditionally think of as ‘deep-sea monsters’: anglerfish, viperfish, gulper eels, vampire squid, giant squid, sleeper sharks, and dumbo octopuses.”
     • Meet a midnight zone native! The angler fish is a bioluminescent creature who uses a light hanging from its head to lure prey (you may recognize them from Finding Nemo). See one in action in this video.
   • Dive into ocean conservation: Carpool, use public transportation, or ride a bike to reduce vehicle pollution. This helps to curb ocean acidification and reduces toxic runoff.
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4

Abyssopelagic Zone (Abyssal Zone)

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1. 
   The abyssopelagic zone accounts for about a third of the planet’s seafloor. “Now we’re entering one of the most extreme environments on Earth,” says Ray. “It is completely dark, extremely cold, and under enormous pressure. Animals here tend to have very specialized adaptations and extremely slow metabolisms because food is scarce.” This zone is made up of trenches, sea mounts, and oceanic ridges and is abundant in valuable minerals like cobalt, nickel, and aluminum.

   • How deep is it? The abyssal zone extends from 4,000 to 6,000 meters (13,100 to 19,700 feet) deep.
   • What are the temperatures? This zone’s average temperature hovers around 36 to 39°F (2 to 4°C).
   • What lives there? Ray names tripod fish, rattail fish, sea cucumbers, deep-sea octopuses, and various crustaceans as inhabitants of this zone. She adds that the tripod fish “can actually use elongated fins like stilts to position itself above the seafloor and wait for food to drift by.”
     • Meet an abyssal zone native! The rare (and adorable) dumbo octopus has lateral fins that resemble ears like the cartoon elephant, Dumbo. Watch this video to see a rare sighting!
   • Dive into ocean conservation: Join the Deep Sea Conservation Coalition’s efforts to protect seamounts, our ocean’s lifelines, by filling out this form to contact government officials who can help end destructive deep sea fishing practices.

5

Hadalpelagic Zone (Hadal Zone)

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1. 
   The hadalpelagic zone refers to deep ocean trenches. “This is the deepest part of the ocean, found primarily inside deep ocean trenches,” says Ray. “It extends all the way down to nearly 11,000 meters in the Mariana Trench.” She adds that the hadal zone is “one of the least explored ecosystems on Earth. Animals living here have to withstand crushing pressure, complete darkness, extreme cold, and limited food.” The buildup of carbon in the base of the hadal trenches may play a vital role in regulating the carbon cycle and the Earth’s climate.

   • How deep is it? The hadal zone extends from 6,000 to 11,000 meters (19,685 to 36,089 feet) deep.
   • What are the temperatures? The temperature is constantly just above freezing at about 34 to 39°F (1 to 4°C).
   • What lives there? Polychaete worms, sea cucumbers, and amphipods are some of the unique creatures cut out for life in the hadal trenches.
     • Meet a hadal zone native! The hadal snailfish is one of the deepest-living fish ever found. Ray says it’s been documented at depths of around 8,000 meters. “These fish look surprisingly different from the stereotypical ‘deep-sea monster,’” she says—instead of huge teeth and glowing lures, they have “soft, gelatinous bodies adapted to enormous pressures.” Check out this video to see a few of them up close!
   • Dive into ocean conservation: Donate to organizations like the Ocean Conservancy and Oceana to help support research and other conservation efforts that will protect our oceans.
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• “These aren’t just arbitrary divisions on a chart,” emphasizes Ray. “Each zone represents a different set of environmental challenges, and evolution has produced completely different solutions to those challenges.”
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• At the same time, Ray says, “these zones are connected. For example, the movement of animals between the surface and deep ocean helps transport carbon and nutrients through the water column. Meanwhile, sinking organic material from the surface provides an important food source for animals living thousands of meters below.”
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