These next shots are Dall’s porpoises. They are compact, muscular porpoises that rival killer whales as the fastest marine mammals in Alaska waters. Their black backs and white bellies and flanks resemble the markings of killer whales, but they are much smaller, averaging about six feet in length and weighing about 300 lbs. (136 kg). They are fast swimmers and often generate a “rooster tail” spray that can be visible at long distances.