Krill oil is oil from a tiny, shrimp-like animal. Baleen whales, mantas, and whale sharks eat primarily krill. In Norwegian, the word "krill" means "whale food." People extract the oil from krill, place it in capsules, and use it for medicine. Some brand name krill oil products indicate that they use Antarctic krill. This usually refers to the species of krill called Euphausia superba.