- Thanks to their ability to swim,
由于会游泳 - jellyfish were the first to venture out of the shallows
水母率先冒险离开浅海 - and into the big blue.
进入巨大的蓝色海洋 - Here, with fish yet to evolve,
在这里 鱼类尚未进化 - jellyfish were entirely free of predation.
水母完全摆脱了被捕食的危险 - In time, others would follow.
随着时间的推移 其他生物也会跟随而来 - But more than half a billion years ago,
但是五亿多年前