Every year, penguins experience a molting process. That is the time when they shed and regrow all their feathers. It would take about a few weeks before all their feathers return. Hence, they cannot swim or hunt within those weeks and rely on what they stored beforehand.
Penguins are fascinating! Molting sounds like such a tough but essential process for them. It's incredible how they prepare by storing up food beforehand. Nature is amazing!