How Long Can Seals Hold Their Breath? Diving Explained

How long do seals stay underwater?

How long a seal can stay down depends on its size, its body chemistry and how deep it feeds. Big, deep-diving species such as elephant seals can hold their breath the longest, while smaller coastal seals make short, shallow dives.

Record dives are rare. Seals normally stay well within their limits, so that they can surface, breathe for a short time and dive again without needing a long rest. NOAA also reports that gray seals can dive to about 475 m (1,560 ft) and for as long as an hour.

Harbor seals: short, shallow dives

The harbor seal feeds mostly in coastal waters, so it rarely needs to dive far. In Alaska, most harbor seal dives are less than 20 m (65 ft) deep and shorter than 4 minutes, and dives of 3–7 minutes are typical elsewhere. When they need to, harbor seals can dive to about 500 m (1,640 ft) and stay down for 30 minutes or more.

Pups learn quickly. Harbor seal pups can swim within minutes to hours of birth, and NOAA reports that they can dive for up to about 2 minutes when only 2–3 days old.

Elephant seals: the champion divers

The northern elephant seal spends about nine months of the year at sea and most of that time underwater. NOAA describes dives to about 300–760 m (1,000–2,500 ft) lasting 20–30 minutes, separated by only short breaks at the surface, often just 2–3 minutes. Tagged females have been found diving almost nonstop for 20 hours or more a day.

Males and females hunt differently. Males tend to dive to the seafloor along the continental shelf, while females hunt squid and fish in the open ocean and dive deeper, on average about 500 m (1,640 ft). The deepest dive recorded for the species is about 1,735 m (5,692 ft), and dives of more than an hour have been recorded. Its southern relative holds the seal records: about 2,388 m (7,835 ft) deep and close to 2 hours long.

How do seals hold their breath so long?

Seals do not simply have big lungs. In fact, true seals usually breathe out before they dive. Their secret is storing oxygen in the body and using it very slowly.

• Lots of blood. Seals have a large volume of blood rich in hemoglobin, the oxygen-carrying protein. In deep divers such as elephant seals, blood can make up about 20% of body weight, roughly three times the share in a human.
• Oxygen in the muscles. Seal muscles are packed with myoglobin, a protein that stores oxygen, which makes their muscles look very dark, almost black.
• A spare tank in the spleen. Elephant seals store oxygen-rich red blood cells in a large spleen, which contracts during a dive and releases them into the blood.
• The diving response. When a seal dives, its heart rate drops sharply and blood vessels to the skin, gut and other organs narrow. Oxygen is kept for the brain and heart, the organs that need it most.
• Saving energy. Seals glide whenever they can. At depth their bodies become less buoyant, so they can sink with little effort instead of swimming.

Breathing out before diving has another benefit. As the seal descends, water pressure squeezes its small amount of remaining air out of the lungs and into the windpipe and larger airways, where little gas can pass into the blood. That limits the nitrogen the seal absorbs and helps it avoid decompression sickness, the “bends” that can affect human divers.

Do seals sleep underwater?

Yes, and elephant seals do it in a remarkable way. A study published in 2023 recorded the brain activity of northern elephant seals at sea and found that they slept about 2 hours a day, much less than most mammals. They took naps of less than 20 minutes during deep dives, spiraling slowly downward like a falling leaf, sometimes to depths of about 377 m (1,237 ft), where they are safer from orcas and sharks that hunt near the surface.

Harbor seals can sleep at sea as well, either floating upright with only the head above the water, a posture often called bottling, or resting underwater and surfacing now and then to breathe. Close to the coast, though, they usually prefer to haul out and sleep on rocks or sandbanks.

How do seals compare with other divers?

Seals are among the best divers of all mammals, but some whales go further. Sperm whales and beaked whales can dive deeper and stay down longer, as described in How deep can whales dive? Seals easily outlast smaller diving mammals such as otters, whose limits are covered in How long can otters hold their breath?

People are no match. Most of us cannot hold our breath for more than a minute or two, and even the best trained freedivers, resting motionless in a pool, have managed only between 11 and 12 minutes. A harbor seal can beat that on a long dive while swimming and hunting, and an elephant seal can stay down for more than an hour on one breath.