Respiratory System

The main differences between the typical mammalian respiratory system and the penguin respiratory system has a distinct feature, which is its lack of a diaphragm. This means there is a continuous cycling of air, and they have air sacs. 
The little penguin has circular respiration. You can tell because the air is constantly moving through the lungs with fresh oxygen. Instead of breathing in and out like humans, air flows consistently over the oxygen-blood exchange barrier. This proves to be a very effective way to extract oxygen. Penguins need this to "fly" through the water finding food.