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.