His time down here is limited by how long he can hold his breath. 它在水下的时间 受限于它能屏住呼吸的时间

279. But unlike whales, they still spend much of their time lazing on land.
     但与鲸不同 它们多数时间仍懒洋洋地躺在陆地上
280. It's in the water that they come alive...
     在水中 它们才会活跃起来
281. chasing schools of fish.
     追逐鱼群
282. His time down here is limited by how long he can hold his breath.
     它在水下的时间 受限于它能屏住呼吸的时间
283. He seems caught between two worlds,
     它似乎夹在两个世界之间
284. especially when facing danger.
     尤其是面临危险的时候
285. The mammal's intelligence is his only defense...
     哺乳动物的智慧是它唯一的防御手段

来自《我们星球上的生命 第一季 第七集 Life on Our Planet S01E07 地球继承者》第 282 行