What are the features of the body structure of penguins in connection with their adaptation to their habitat?

Penguins are large flightless birds that live in cold climates.
Penguins are swimming birds and, therefore, have a body adapted to the aquatic environment: a streamlined body shape, webbed hind limbs and wings that have evolved into flippers.

Due to the cold habitat conditions, these birds have warm plumage without bare skin and they have a thick layer of subcutaneous fat in order to more easily tolerate low temperatures. Penguin feathers are tough, which makes it possible not to get wet in the aquatic environment.