I’ve mentioned how penguins are pretty special birds, but I couldn’t resist posting again about their incredible adaptations as swimmers. On land they strut and waddle and trip and jump and generally look adorable and a little bit ridiculous… but as soon as their flippers strike the water, they transform.

Here’s a list of the ten coolest penguin adaptations/exaptations that allow them to swim like Olympic champions (or significantly better, sorry Michael Phelps…) in order of crazy awesomeness (aka no particular order):

1. Penguins are fat. Literally, according to NatGeo Wild and a study on Adelie penguins, the different species are all over 1/3 fat when they begin the breeding season. Although they lose much of this fat between feeding trips (King penguins can lose 50% of their body weight in a few weeks), the remainder helps insulate the birds from the extremely cold water.

2. Penguins are not fuzzy. The key to warmth in dry places is trapped air, and it’s the same in the water. But this means that penguin chicks (don’t worry, more photos to come) with their fluffy feathers don’t do so well when the feathers get wet. Meanwhile, adult penguins spread a greasy covering from a gland near the tail over their overlapping and interlocking body feathers that effectively waterproofs the birds’ internal coats of down, very analogous to our expedition’s giant orange coats over many layers of polar fleece. But as the penguins dive, they must feel the cold more and more as the limited air in their feather coat compresses and becomes a less effective insulator, much like human divers in their wetsuits and drysuits (Hi Justin and Erin!). They can’t keep too much air in their feathers or they’ll be too buoyant to dive. What they need is heated undergarments.

3. Penguins are countershaded. While the dark-on-top light-on-bottom coloration makes them look awfully dapper, penguins likely also use this coloration for heat regulation on land and camouflage at sea. Looking up at white bellies or down at black backs is more difficult for predators, allowing penguins to blend in just a little with the sky and darker ocean depths. This may also help them catch their prey.

4. Penguins hold their breath. Emperor penguins can dive for over twenty minutes, rising to the surface with blood oxygen levels so low that other animals would have passed out or experienced tissue damage well before they reached the open air. Not all penguins are so deep-diving- some average dives of thirty seconds or so- but all penguins have increased hemoglobin and myoglobin in their blood and tissues to help store oxygen.

5. In terms of oxygen efficiency, it also doesn’t hurt that penguins can regulate bloodflow to the exposed parts of their bodies (extremities like feet and wingtips, bare patches of skin on the face, etc.) as the water chills those body parts and slows metabolism and oxygen demand.

6. Speaking of blood, a penguin’s veins wrap around their arteries, transferring heat into the arterial blood and conserving as much of that precious internal body temperature as possible.

7. Penguins are streamlined. This doesn’t require much explanation- they’re like little well-dressed torpedoes, heads shrunk into shoulders and feet stretched back near the tail for steering and maneuverability.

8. Penguin wings are no good for flying, obviously- too tiny and stiff. But they’re AWESOME flippers underwater, attached to strong breast muscles to beat against the dense cold water. Penguin breast bones are very impressive. The photos I have of penguin bones are sort of gruesome, so I won’t post them, but you can search for them if you want.

9. Penguins can drink salt water! I know I’ve talked about this before, but I still think it’s really cool that they have a special gland for removing much of the salt out of ocean water. They just sneeze it out and continue about their badass way.

10. With such stubby wings, penguins already couldn’t fly. But with no need for lightness of body and a good incentive to dive deep, penguins have evolved away from hollow bird bones to solid bones, dense and sink-y.