The porpoises are small cetaceans of the family Phocoenidae related to whales and dolphins. They are however distinct from dolphins, although the word "porpoise" is often used to refer to any small dolphin, especially in North America. A key difference is the shape of the teeth and of the head. Porpoises, divided into six species, live in all oceans, mostly near the shore. Probably best known is the Harbor Porpoise, which can be found across the Northern Hemisphere. Porpoises tend to be smaller but stouter than dolphins. They have small, rounded heads and blunt jaws instead of beaks. Their teeth are spade-shaped, whereas dolphins have conical teeth. In addition, a porpoise's dorsal fin is generally triangular, rather than curved like that of many dolphins. These animals are the smallest cetaceans, reaching body lengths up to eight feet with the smallest species being the Vaquita, reaching up to five feet in length. Porpoises are predators hunting mainly fish, often also squid and crustaceans. Most common are small groups of up to ten individuals, which in some species may join forming aggregations of several hundred animals. This series of "Marine Life Protection" proof one dollar coins has been a hit with collectors since the first coin was issued in 1992. It is hard to say whether the obverse or reverse is the most attractive, but they are becoming exceedingly hard to find. Palau was chosen as the location for the 10th season of the hit reality series Survivor, and this coin depicts regional marine life, as well as a beautiful mermaid. This One Dollar coin is legal tender and has been issued by authority of the government of Palau.