The yellow-bellied sea snake has a paddle-like tail and a laterally compressed body that gives an eel-like appearance. Unlike fish, it does not have gills. Like all reptiles, it breathes air and must surface regularly for respiration. It is among the most completely aquatic of all air-breathing vertebrates. As noted above, the yellowbelly possesses one of the most potent venoms of all snakes. The yellowbelly is the most widely distributed sea snake and is capable of living and giving birth entirely in the open sea (that is, it is totally pelagic). It is found in all coastal waters around the rim of the Pacific Ocean except Alaska south to southern California, and in the coastal waters of the Indian Ocean from the Persian Gulf eastwards. It is the only sea snake to have reached the Hawaiian Islands. The sea snake has also been reported around the shores of New Zealand, a country that would otherwise be free of snakes were it not for the infrequent visits of yellowbellies. The yellow bellied sea snake can grow up to three feet long. Its head is narrow, with an elongated snout; its nostrils are on the top of its head, and nasal shields are in contact with one another. Colors of the snake are variable, but most often distinctly bi-colored, with black above and yellow below, with the dorsal and ventral colors sharply demarcated from one another. On its stomach, there may be a series of black spots or bars on the yellow background, or the yellow may extend around its back so there is only a narrow mid-dorsal black stripe, or a series of black crossbars.