Some of the young have even taken to underwater swimming. They can stay down for more than 30 seconds and appear to do this just for fun. Yet these swimming skills acquired during play will certainly be useful later in life in these flooded mangrove forests. In cooler climes, mud, laid down in estuaries, is colonised by salt marsh grasses and form one of the most productive habitats on the planet. 400,000 greater snow geese flock to the estuaries along the Atlantic coast of the United States to rest and refuel on their long migratory journeys. This is the end of the river's journey. Collectively they've worn down mountains and carried them to the sea. And all along the way, their fresh water has brought life and abundance to planet Earth.


有些小猴甚至可以潜水游泳。它们可以在水下呆30秒，不过看来这仅仅是为了好玩。但是，这种在玩乐时学会的游泳本领，在日后红树林被淹时无疑是非常有用的。在较凉爽的地区，河口淤积处生长着盐沼植物，也成为地球上最适合于生物栖居之地。40万只雪雁聚集在美国大西洋岸边的河口，它们于长途迁徙途中在这里休息并补充营养。这里是河流的出海口，它们一起冲破了高山，把沉积物带到了大海。一路上它们的淡水给我们的地球带来了丰富的生命。