The Deep Sea

by The Ocean Portal Team

A deep-sea octopod wraps itself around a submersible’s robotic arm in the Gulf of Mexico.


2007 Woods Hole Oceanographic Institution, All Rights Reserved

Deep below the ocean’s surface is a mysterious world that takes up 95% of Earth’s living space. It could hide 20 Washington Monuments stacked on top of each other. But the deep sea remains largely unexplored. Dive down 650 feet (one monument or 200 meters), and you notice that light starts fading rapidly. Dive deeper: the temperature drops and pressure rises. At 13,000 feet (20 monuments or 4,000 meters), the temperature hovers around freezing, and there’s no sunlight at all. Yet there is life -- an astounding variety of creatures that will boggle your mind. You can’t dive to the deep ocean on your own, of course. But scientists now have a variety of sophisticated technologies to explore this vast frontier. What they’re finding will amaze you.

What Lives Here


Giant eyes spot prey. Huge claws grab the prey, and a tiny mouth rips it to shreds.


© David Shale

It’s hard to imagine a more forbidding place than the icy cold, pitch black, crushing environment of the deep ocean. It’s even harder to imagine anything living there. But researchers are discovering that thousands of fascinating animals—including fishes, corals, crustaceans, jellyfishes, and worms—have adapted to life in this challenging environment.

Many of these animals look quite alien to us. Some have huge eyes—or eyes on long stalks—that capture the little existing light. Others seem to be all mouth. Their gaping jaws—often filled with fanglike teeth—are always open, ready to capture whatever morsels fall from above. Still other deep sea animals have transparent bodies that you can see through, enabling them to blend right in to the waters.

Research & Exploration

Census of Marine Life

Making Ocean Life Count

Census researchers discovered this sea cucumber (Enypniastes sp.) in the Gulf of Mexico.


Laurence Madin, Woods Hole Oceanographic Institution/CMarZ, Census of Marine Life

It seems like a herculean task to figure out what lives in something as vast as the ocean. But the 10-year-long Census of Marine Life project studied just that question. This network of scientists from more than 80 nations worked to document the diversity, distribution, and abundance of life in the oceans—past, present, and future. So far researchers have discovered more than 5,000 new species. And they expect to find many more as the research continues beyond the program's official end in 2010.

The Census explored ocean life from top to bottom, pole to pole, microbes to whales. Several field projects focused on deep ocean habitats—seamounts, hydrothermal vents, the ocean floor, and the waters around the Mid-Atlantic Ridge. Project results continue to play a critical role in deciding how to manage this valuable global resource.

Ocean Drilling

Drilling Beneath the Ocean Floor

This Japanese research ship drills into the ocean floor to learn about Earth’s history and structure.


Adapted from JAMSTEC & Brian T. Huber/Smithsonian Institution

In Japanese Chikyu means “Earth” — and that’s what this formidable research vessel, completed in 2005, was designed to study. It can drill up to 23,000 feet (7,000 meters) below the ocean floor to obtain sediments from Earth’s crust. No other research ship has ever drilled that deep. The derrick holding the Chikyu's drill stands 328 feet (100 meters) high — the tallest in the world. It is the only ship in the world able to drill into earthquake zones. And one day, researchers hope, it will be the first ship to drill all the way to Earth’s mantle.

The Chikyu is part of the Integrated Ocean Drilling Program (IODP), a marine research program supported by 24 countries. By collecting and analyzing sediments from below the seafloor, IODP is increasing our understanding of Earth’s history, structure, and changing environment.

Tools & Technology

Technologies for Exploring the Deep

The research submersible Alvin uses bright lights to illuminate the dark seafloor.


Pat Hickey/Woods Hole Oceanographic Institution

No place on Earth is as distant or as alien as the deep ocean. But we’re now able to explore more and more parts of this remote realm—thanks to a new generation of incredible underwater vehicles.

Some vehicles—known as human occupied vehicles (HOVs)—carry scientists themselves to the deep sea to see firsthand what’s there. Other kinds of unmanned craft let scientists see and study those places they can’t go. For example, scientists can steer remotely operated vehicles (ROVs) from ships at the surface. A cable links the ships to the ROVs, limiting their mobility. Autonomous underwater vehicles (AUVs) have no cable, but they need to be pre-programmed. A new breed of hybrid vehicles (HROVs) combines the best features of ROVs and AUVs: They can have a surface operator, or drop the cable and go it alone.


Smithsonian Collections

The Case of the Mystery Squid

A Smithsonian specimen helped identify a new family of deep sea squid with long spindly legs.


From Vecchione, M., R. E. Young, A. Guerra, D. J. Lindsay, D. A. Clague, J. M. Bernhard, W. W. Sager, A. F. Gonzalez, F. J. Rocha, M. Segonzac. 2001. Worldwide observations of remarkable deep-sea squids. Science 294(5551):2505-2506.

What do you do with a squid that doesn't belong? In 1995, a collection of eastern Pacific squids was donated to the Smithsonian -- but one specimen didn’t fit into any known family of squids. It had wide fins that looked almost like elephant ears, and skinny arms that had been severed a few inches below the squid's mantle. Together with a slightly larger juvenile specimen in the collections and a paralarva (baby) from Hawaii, this odd-looking specimen led to the identification of a whole new family of squids: the Magnapinnidae, or bigfin squids.

But that wasn't the end of the story.

A few years later, researchers in deep-sea submersibles began spotting large and very strange squids. They had long spaghetti-like arms -- reaching 20 feet (7 meters) -- that bent like elbows. They were so unusual they were nicknamed “mystery squid” by Smithsonian and NOAA researcher Dr. Michael Vecchione.

By comparing videos of these “mystery squid” with the juvenile bigfins in the Smithsonian’s collection, scientists identified the strange squids as adult bigfins. With the help of long-dead specimens, a modern-day mystery was solved.

Deep Ocean Corals

Stephanocyathus (A.) spiniger, a solitary, deep-water stony coral species, has six long spines that slow it from sinking into soft substrates.


Smithsonian Institution

There are millions of animals in the Smithsonian collections. Many of the specimens—including these solitary corals—came from the deep ocean. Although they’re now dead and colorless, they have a lot to teach us about life in the sea today.

For example, as a quick glance at the collection cards shows, deep ocean specimens tell us where and at what depths particular species live. By comparing specimens collected at different times, researchers measure variations in a species’ form over time. Today they can even document changes in a species’ genes by extracting DNA from dried tissues. And because the collections were built over many years, they reveal changes in deep sea diversity. As human activities continue to impact the ocean, this knowledge will help us manage this fragile ecosystem.


Dr. Michael Vecchione, Deep Ocean Explorer

Dr. Vecchione served as Chief Scientist on this 2009 expedition to the Mid-Atlantic Ridge.


© David Shale

“Getting in the sub and diving is an awe-inspiring experience,” says Dr. Michael Vecchione. “Every time we go down, we see something new.”

A cephalopod biologist (squid expert), Dr. Vecchione has taken trips to the bottom of the sea and served as Chief Scientist on many deep ocean expeditions. On dry land, he serves as Director of the National Systematics Laboratory, a NOAA Fisheries lab located at the National Museum of Natural History. Recently, as a scientist on the core team for the museum’s new Sant Ocean Hall, he had a chance to share his lifelong fascination with the ocean. “The opportunity to educate six million visitors a year about the ocean was really important to me,” he says.