Krill are shrimp-like crustaceans that are approximately 1 to 6 centimeters long. They live is the ocean, where they feed mainly on phytoplankton. Krill primarily live in the Southern Ocean and the northern Pacific Ocean along the coasts of Canada and Japan. Krill are a rich source of healthy fatty acids. Krill oil contains rich omega-3 fatty acids, which is the main reason it’s becoming popular as a nutritional supplement.