How do penguins stay waterproof in icy waters?

Penguins stay waterproof thanks to their dense, overlapping feathers and an oil they secrete from a gland near their tail. During grooming, they spread this oil over their feathers, creating a waterproof barrier. This prevents water from reaching their skin and helps them maintain body heat in freezing waters. Combined with a thick layer of blubber, this adaptation allows penguins to thrive in cold aquatic environments.