The highest diversity of marine snakes occurs in Southeast Asia and Australasia and coincides with the highest diversity of mangroves. Mangrove forests tend to be highly productive, dynamic ecosystems with tides, rainfall, flooding rivers, and storm surges causing daily and seasonal changes in salinity. Less diverse assemblages of brackish water and marine snakes occur in the Gulf of Guinea, the Neotropics, the Mediterranean, the southeast USA, and the Gulf of California. One reason for the Sunda Shelf diversity seems to be the sheer size of the wetland-marine complex, with an area of more than 1.85 million square kilometers. The ancient Pebas wetland of the western Amazon seems to be responsible for the high diversity of aquatic snakes in the modern Neotropics.