The sei whale (pronounced "say") is found worldwide. They can measure up to 69 feet in length and can weigh up to 40 tons. The body is dark gray with white undersides, usually limited to the area of the throat grooves which do not reach as far as the navel. The sei whale may be the fastest of the large whales, able to cruise at 16 mph and with a maximum speed of 45 mph. Sei whales usually travel alone or in small groups of five or less.