The sei whale (Balaenoptera borealis) is a dark-gray, stream-lined baleen whale that is found worldwide except in polar waters. It swims in small pods of 3-5 whales but larger groups may form at rich feeding grounds. It has very fine grey-black baleen that traps very small particles of food. It is a rorqual whale (a large baleen whale) that is similar to the Bryde's whales.