They're kind of moving around, coming up and under and over.它们只是游来游去,在海平面上上下下
up and down:上上下下; 来回
The lion paced restlessly up and down in its cage.
狮子在笼子里不安地来回走动。
You'd think it'd be quite easy to keep track of a 40-tonne animal.你会以为追踪四十吨的动物蛮简单的
keep track:通晓事态, 注意动向
He reads the newspapers to keep track of current events.
他阅读报纸以了解时事。
We have to keep track of every cent we spend.
我们得记下我们花的每一分钱。
One minute they're there, we get up reasonably close,它们一下子在那里,我们赶紧靠近
get up:变得猛烈;筹备
The wind is getting up.
风越刮越大。
We're getting up a party for her birthday.
我们要给她开生日庆祝会。
then they'll come up again and they'll be 300 yards away,可是却在三百码的距离之外出现
come up:出现
The flowers are just beginning to come up.
花刚开始长出地面。