the sea floor is carpeted with dense mussel beds. 布满了密密麻麻的贻贝

140. This unusual duck pond provides an overnight sanctuary
     这个不同寻常的水池是过夜的庇护所
141. and, when day breaks, a rare chance to feed.
     而且到了白天还有难得的进食机会
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

来自《行星地球 第一季 第六集 Planet Earth S01E06 冰雪世界》第 143 行