The main threats for penguins in water are leopard seals, fur seals, sea lions, sharks and killer whales.
In the late 1800s penguins were often hunted to use their oils. Penguins have a gland that allows oil to be created from the tail.
Little Blue Penguins Underwater in Aquarium
There are quite a few types of predators out there that find penguins to make the perfect meal.
Macaroni Penguin in Aquarium