crocodiles must strike with lightning speed. 鳄鱼必须以闪电般的速度出击

115. once they have a hold, they never let go.
     一旦被它逮住 猎物再无逃脱的机会
116. It took over an hour to drown this full-grown bull.
     它得花上一个多小时 才能淹死这只成年公角马
117. To surprise their prey
     为了突袭猎物
118. crocodiles must strike with lightning speed.
     鳄鱼必须以闪电般的速度出击
119. Here, only the narrowest line separates life from death.
     在这里 生与死只有一线之隔
120. Most rivers drain into the sea,
     大部分河流都汇入大海
121. but some end their journey in vast lakes.
     可有些河流的终点却是大型湖泊

来自《行星地球 第一季 第三集 Planet Earth S01E03 淡水》第 118 行