Many species of cetaceans, (whales, dolphins, and porpoise), inhabit or migrate through Alaskan waters. Several pods of orcas, (killer whales), reside in the Prince William Sound area and humpbacks can be spotted in the western portion mid-May through September. Two populations of beluga, (white whales), live in Alaska; one group inhabits Cook Inlet and can be seen in the Port of Anchorage as well as in Turnagain Arm from the road system midsummer through November. The Bering Sea population can be viewed around the mouths of western Alaska rivers during the summer and sometimes for miles upstream. Bowheads come close to shore around Barrow in April or May and return as they migrate past in August through October. Humpback whales and orcas are found throughout the Inside Passage, (Southeast Alaska), during most of the year and minke whales are also occasionally sighted. While boat tours offer the best chances to spot them and the closest viewing opportunities, many species can also be viewed from shore.

Though orcas, humpbacks, and belugas are the most frequently seen large cetaceans in Alaska, many other species spend at least part of the year in Alaskan waters. Gray whales migrating from Baja California pass along the outer coast of Southeast Alaska on the way to summer feeding grounds in the Bering Sea. In addition to viewing opportunities during migration, some individuals occasionally remain along Southeast Alaska's outer coast for the summer. Many species that prefer the open ocean over coastal areas also visit Alaska to feed during the summer; these more pelagic whales include blue, fin, sei, minke and sperm whales, some of which are occasionally viewed from whale watching boats departing from the Kenai Peninsula. Dall's porpoise, harbor porpoise, and Pacific white-sided dolphins are also frequent encounters in certain areas of the state.

Marine mammals other than cetaceans offer frequent encounters in Alaska, often in the same areas visited by whale watching boats. Fur seals are found on the Pribilof Islands, walrus congregate around Nome in May, and Steller's sea lions, harbor seals and sea otters inhabit many areas of Alaska along with less conspicuous animals like river otters and mink. Passengers on wildlife viewing boats often see these animals in addition to a large variety of marine birds.

For a variety of articles on marine mammals, visit this Fish & Game site.