10. Roughly 172,000 narwhals are swimming in the Arctic today.

A narwhal is a toothed whale and is closely related to dolphins, porpoises, and orcas. They live and travel in pods that range in size from a few narwhals to several hundred individuals, but the congregations can be in the thousands in the summertime. Females, young, and immature males live together, and adult males live in their own pods. They have a famous tusk that is actually a specialized tooth that protrudes out of the left lip, and in rare cases, a narwhal can have two.

While all males have tusks, only 15 percent of females have a tusk. The longest tusks can reach over eight feet long. Understanding the function of the tusk is an ongoing area of investigation. One of the narwhal’s unique talents is diving. They are some of the deepest diving whales, with a record dive of over a mile deep! They are also excellent at conserving oxygen as their muscles are built to minimize oxygen use and simultaneously carry large amounts of oxygen. Interestingly, during the deepest dives, a narwhal can shut off oxygen flow to unessential organs and instead divert it to where it is needed most.

9. Antarctic ice fish have blood with built-in antifreeze.

In oxygen-rich Antarctic waters, ice fish can survive and thrive in freezing waters. They have no hemoglobin, which is the oxygen-carrying protein that makes red blood cells red. In the absence of hemoglobin, the gills of ice fish appear white. The ice fish instead have special blood that contains proteins that act like antifreeze. The ice fish usually have ice crystals inside their bodies, and the special proteins work to ensure that the crystals do not grow in size. Surprisingly, researchers have found that ice crystals do not go away during the warmer summer months, which is one of the implications of living below the ice. This unique antifreeze protein is also found in a group of more than 120 fish that live in the Southern Ocean.

8. Arctic cod can thrive in frigid waters.

Arctic cod are a rare breed that is able to live in water that is cooler than the freezing point of blood. Although most commonly associated with ice, such as in the White Sea, Arctic cod is also present in ice-free nearshore waters in Alaska. Similar to Antarctic ice fish, Arctic cod have an antifreeze protein that keeps their blood flowing even in the coldest of waters. Arctic cod are critical players in the Arctic food web. They contribute by eating small crustaceans, such as amphipods and copepods. In turn, Arctic Cod are food for seabirds and many marine mammals. Due to the unpredictable conditions, Arctic cod have early maturity, rapid growth, production of large numbers of offspring, and a shorter life span.

7. Orcas can be found in both the Arctic and the Southern Oceans.

Orcas, also known as killer whales, tend to stay put in their distinctive ecosystems. There are different characteristics of the groups, or pods, in various locations. Although all orcas are considered the same species, some thought they might be other species among the pods in Antarctica or at least subspecies. They are the largest of the dolphins and powerful predators. Uniquely, orcas can travel in pods of up to 40 related individuals. These traveling pods act like wolf packs by working together to take down their prey, including seals and larger whales.

Killer whales communicate through a wide range of sounds, and each pod has a signature audio sound that pod members can recognize from far away. In orca populations, knowledge is passed down to younger individuals from their elders. This concept includes what to eat and where to find it, how to catch it, whom to avoid, vocalizations, and calls that are unique to pods and family groups. Having multiple prey items to choose from likely led to the niche specializations we see today.

6. Leopard seals are able to survive in some of the world’s coldest waters.

These types of seals are named for their black-spotted coats. The pattern is similar to that of the famous big cat, although the seal’s fur is gray rather than golden. Leopard seals are also referred to as sea leopards. They are fierce hunters with powerful jaws and large, muscular body. The patterned fur on their bodies is dark on the top and lighter on their underbellies. The fur acts as a camouflage in the water, enabling them to hunt down fish, penguins, squid, and smaller seals with ease.

They often wait underwater near an ice shelf and snare the birds just as they enter the water after jumping off the ice. They may also come up beneath seabirds resting on the water’s surface and snatch them in their jaws. In comparison to other seals, leopard seals are earless seals with long bodies and elongated heads. To survive and thrive in the cold waters, a thick layer of blubber provides them insulation and protection.

5. Opah fish are no strangers to frigid temperatures.

The opah, also known as the moonfish, has relatively small red fins decorating its large, round body, growing up to six feet long. The fins, which flap rapidly as the fish swims, become essential in generating body heat for the opah. This fish has a countercurrent heat exchange system in its gill tissue to cope with such frigid conditions. This system allows it to maintain a body temperature that exceeds the surrounding water’s temperature by approximately 41 degrees Fahrenheit.

Therefore, the opah is warm-blooded, which makes it unique amongst fish species and allows it to remain active even in near-freezing water. The increased temperature speeds up physiological processes within the body. As a result, the muscles can contract faster, the eye’s temporal resolution is increased, and neurological transmissions are sped up. This notion means they have faster swimming speeds, better vision, and quicker response times.

4. Emperor penguins are the tallest and largest of all the penguins.

These penguins are one of nature’s great survivors and are exclusively found in the Antarctic. There, the water temperatures remain around the freezing point for saltwater. To cope with the Antarctic weather, emperor penguins have the highest feather density of any bird species, with around 100 feathers covering one square inch of skin. In the water, these feathers flatten to create a waterproof outer layer, which protects the penguins’ insulating down from becoming saturated with cold water.

They also huddle together in tightly packed groups to conserve heat and shelter themselves from the intense winds. Occasionally, these huddles can be too good at keeping the emperor penguins warm. The penguins on the outside of the huddle regularly muscle their way inside as they face the direct hit of Antarctica’s icy wind chill. In addition, the penguins on the inside get too hot, so after a while, they need a little room to cool off.

3. Greenland sharks have been observed at depths of up to 7,200 feet.

Found in the sub-Arctic, Greenland sharks can survive the near-freezing temperatures of these waters thanks to a compound called trimethylamine oxide. This compound acts as a natural antifreeze and prevents ice crystals from forming in the sharks’ bloodstream. This compound also makes Greenland shark meat poisonous to humans and other mammals, so this species has no natural predators. Greenland sharks are among the most massive sharks globally and have been known to grow as long as 21 feet long.

Greenland sharks are not spotted frequently because of their ability to dive to such extreme depths. Not only can they dive as deep as 7,200 feet, but they also sometimes can be found relaxing on the slopes and shelves far under the ocean’s surface. Although all sharks are cold-blooded, this particular species truly thrives in a frigid environment. They always migrate to the coldest part of the water each season. In fact, Greenland sharks are the only known shark species that can tolerate Arctic conditions all year long.

2. Antarctic sea spiders’ legs can grow to span the width of your face.

Like all marine invertebrates, Antarctic sea spiders have a body composition that matches the ocean’s salinity, which means that as long as the water around them remains in liquid form, they cannot freeze. Antarctic sea spiders are considerably larger than temperate sea spiders, having an average leg span of 29.5 inches! It is thought that this polar gigantism occurs due to the heightened levels of oxygen found in cold water. Sea spiders are bizarre. They feed by sticking their proboscis into soft animals and sucking out the juices. These sea creatures do not have much room in their bodies, so their guts and reproductive organs reside in their spindly legs. They also do not have gills or lungs. To cope, they absorb oxygen through their cuticle or shell-like skin.

1. Tardigrades — swimming water bears — are almost indestructible.

Also known as water bears, tardigrades are microscopic animals found in some of the world’s most extreme environments, including the deepest ocean trenches and under thick sheets of ice. They have eight legs and hands with four to eight claws on each. These animals can withstand exposure to absolute zero temperatures. Tardigrades survive by replacing most of their internal water with sugar trehalose, which prevents them from crystalizing and damaging cell membranes.

They are also able to reversibly suspend their metabolism, a phenomenon known as natural cryopreservation. They can even survive the chilling conditions by going into an almost death-like state called cryptobiosis. These sea creatures curl into a dehydrated ball, known as a tun, by retracting their head and legs. The tardigrade can come back to life in just a few hours. Tardigrades can also make many antioxidants, which is another way to protect their vital organs from freezing waters.