The ducks must quickly prise the mussels free before the tide starts to turn. 绒鸭必须赶在潮流转向之前迅速采食

142. Just 10 metres beneath the ice,
     就在离冰面10米以下的海底上
143. the sea floor is carpeted with dense mussel beds.
     布满了密密麻麻的贻贝
144. These can only be reached during a brief lull in the currents.
     这个地方只有在洋流暂时停歇时才能吃到
145. The ducks must quickly prise the mussels free before the tide starts to turn.
     绒鸭必须赶在潮流转向之前迅速采食
146. The window of opportunity is short.
     机会之窗随时可能关闭
147. As the current begins to build, it's up, up and away.
     洋流开始转强时它们就只好远走高飞了
148. These permanent holes in the ice provide seafood throughout the winter.
     这个长年不冻的水窟窿提供了整整一个冬天的食物

来自《行星地球 第一季 第六集 Planet Earth S01E06 冰雪世界》第 145 行