Penguins can swim fast, but one number is not enough.
“Cruising” and “bursting” are different things. Many penguins moving steadily underwater are in the range of a few to around ten kilometers per hour. That is already far faster than their walk on land.
If you ask for the fastest penguin, the usual answer is the gentoo penguin. Its body is streamlined, the flippers are powerful, and it can accelerate quickly when chasing prey or escaping danger. Common references put its burst speed around 36 km/h.
But that is not the speed of every penguin on an ordinary swim. Using a fastest burst as the general penguin speed would be like using a human sprint record as the speed of a morning commute.
The real story is the whole underwater body system. Wings became flippers, the body became torpedo-shaped, feathers lie tight, and the feet sit back for steering. Penguins are not fast like flying birds. They are fast like seabirds built for water.
So remember it this way: ordinary speed depends on context, gentoo is the usual fastest example, and 36 km/h belongs in the short-burst category.
The bird that looks slow on shore changes rules once it enters the sea. That is when penguins come closest to flying underwater.
FAQ
Which penguin is the fastest swimmer?
Gentoo penguins are usually listed as the fastest penguins, especially for short underwater bursts.
Do penguins normally swim at 36 km/h?
No. That kind of number should be treated as a short burst or record-style figure, not an ordinary cruising speed.
Why can penguins swim so fast?
They have streamlined bodies, stiff flippers, dense feathers, and diving muscles. For the tradeoff behind that body, see why penguins can't fly.
