Are Penguins the Only Birds That Swim But Can't Fly?

It's one of those "facts" that gets repeated so often it feels true: penguins are the only birds that can swim but not fly. The reality? Penguins have plenty of company in the flightless-but-fabulous-swimmers club.

Meet the Other Flightless Swimmers

The flightless cormorant of the Galápagos Islands gave up flying entirely, evolving tiny, useless wings while becoming an underwater hunting machine. Steamer ducks in South America paddle furiously across water but can't get airborne. Several species of grebes, particularly in isolated lakes, have also lost the ability to fly while maintaining their diving prowess.

Even some rails and coots on remote islands evolved flightlessness while keeping their swimming skills sharp. When you live on an island with no predators and abundant aquatic food, who needs flight?

Why Penguins Get All the Credit

Penguins dominate this narrative for good reason—they're the most spectacular example. Their wings evolved into powerful flippers, transforming them into the fighter jets of the underwater world. Emperor penguins can dive over 1,800 feet deep and hold their breath for more than 20 minutes. They didn't just abandon flight; they reinvented their entire body plan for aquatic excellence.

The other flightless swimmers are either rare, geographically isolated, or less charismatic. A Galápagos cormorant just doesn't have the same brand recognition as a tuxedo-wearing penguin waddling across Antarctic ice.

The Trade-Off That Makes Sense

Here's the fascinating part: flight is expensive. It requires massive chest muscles, hollow bones, and a lightweight frame—all of which compromise swimming ability. Birds that commit fully to aquatic life can develop denser bones for diving, bulkier muscles for propulsion, and body shapes optimized for hydrodynamics rather than aerodynamics.

• Penguins can "fly" underwater at speeds up to 22 mph
• Their bones are solid, unlike flying birds' hollow bones
• They can store more oxygen in their muscles for deep dives
• Their streamlined shape minimizes drag underwater

So while penguins aren't unique in being flightless swimmers, they're certainly the most committed to the lifestyle. They're the overachievers of the flightless swimming world—but they're not alone in the club.