Sea snakes evolved in the Coral Triangle region of Southeast Asia 6 to 8 million years ago, with the majority of species appearing between 1 and 3 million years ago. By the time any sea snakes spread across the Pacific to the New World, the Isthmus of Panama had already closed, blocking their access to the Caribbean. In the Eastern Hemisphere, forbiddingly cold, dry conditions at the tip of South Africa where the Indian and Atlantic Oceans meet prevent the snakes from surviving long if they drift west of the Cape of Good Hope. The snakes die in water colder than 65 degrees, and they depend on the freshwater of rivers, streams, estuaries and rainfall for drinking water.