We know it’s hard to imagine flocks of penguins flying overhead, but millions of years ago penguins did fly.
Eventually, though, flying became superfluous to their lives. They didn’t have any land-bound natural enemies that would make fast escape by air necessary, and they spent most of their time in the water.
Air wings gave way to flipper-like water wings, a change that made penguins able to “fly” through water using the same motions that other birds use to transport themselves through the sky.
Swimming underwater, they can average about eight miles per hour (with bursts of up to 25 mph), “dolphining” up into the air every minute or so to breathe.