PLANET EARTH Freshwater

Crab-eating（捕食蟹） macaques（恒河猴） are mangrove specials. In Indonesia these monkeys have adopted a unique amphibious lifestyle - they fish out fallen food. The troop（成群的） also uses the waters to cool off during the heat of the day. But the channels are also the playground for restless young macaques. 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（河口，入海口）, is colonized by salt marsh grasses and form one of the most productive habitats on the planet.



400,000 greater snow geese flock（成群） 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.
该episode中出现的不同的动物群的用法：
flock多用于鸟类
troop，多用于哺乳动物类
shoal本身就表示鱼群的意思，同时有浅滩；沙洲；潜在的危险；大量的 意思
gang，帮派等，多用于人，用于动物，指代有一定社会性的，或者和人有某些共性的动物