I presume everyone's seen those docos where clumsy looking emperor penguins launch themselves out of the water metres up ice ledges. If you've seen any underwater shots of them doing this, you might have seen those trails of bubbles following them.
Now we know how they do it. They deliberately create those air bubbles to reduce drag. Very impressive.
(My bold.)The mesh-like network of feathers causes tiny bubbles to be formed, and these tiny bubbles coat the entire surface of the penguins, creating a turbulent boundary layer that lubricates the penguin against any drag it may otherwise experience.
It’s pretty much the perfect ‘torpedo-like’ scenario – penguins are utilizing the principles of physics more efficiently than the most capable marine engineers of the human race!
Biology, meet physics: Torpedo-like Emperor Penguins can show us a thing or two about air lubrication... | Dr. Carin Bondar