Penguins and humans share similar ability when it comes to breathing underwater. Like humans, penguins also cannot breathe underwater. Penguins cannot breathe underwater because they do not have gills. When they are in the ocean in search of prey they have to hold their breath. The duration of which they can hold their breath depends on the species.
Penguins have to go airborne to breathe and dive in to continue the hunting. Some penguin’s food may be available in the minimum reach in the ocean but certain species which prey on krill, squid, and fish have to dive deeper into their food.