enable it to soar through the water, with the least expenditure of energy. 可以让它花费很小的力量在水里巡游

45. The shark can find prey far more easily than they can
    鲨鱼比它们更容易发现猎物
46. and they'll be able to collect the scraps from it's meals.
    引水鱼就收集鲨鱼咬碎的食物碎片吃
47. It's long, fixed pectoral fins
    它的长长的垂直的胸鳍
48. enable it to soar through the water, with the least expenditure of energy.
    可以让它花费很小的力量在水里巡游
49. This shark has found a school of rainbow runners.
    鲨鱼发现了一群香蕉鱼
50. It would eat one, given the chance
    这给了鲨鱼一个机会
51. but rainbow runners are swift and agile and not easily caught
    但是香蕉鱼游的敏捷迅速,白鳍鲨不容易捉到

来自《行星地球 第一季 第十一集 Planet Earth S01E11 海洋深处》第 48 行