该湖湖水很深，游泳者探不到底。

The lake is deep and a swimmer cannot touch the bottom.

youdao

水非常深，她见不到底。

The water was very deep and she could not see the bottom.

youdao

掉啊，掉啊，掉啊，难道永远掉不到底了吗？

Down, down, down. Would the fall NEVER come to an end!

youdao

The problems that Frost poses are problems of interpretation, - problems that provoke you to ask not, "what does he mean exactly?

弗罗斯特给我们的困难是翻译，是使人不发问这样的问题，“他到底要说什么“

耶鲁公开课 - 现代诗歌课程节选

I chose English Literature because when I started off a university, I didn't know what it was I wanted to do.

我选英语文学是因为当我刚上大学的时候，我不知道自己到底想做什么。

为何选那门专业？ - SpeakingMax英语口语达人

And you remember Yeats in "The Second Coming," - there's a beast that's kind of-- He doesn't know what it is, and here he's saying something similar.

你们记得在二次圣临里“,有提到一只野兽-,他不知道那到底是什么，在此他表达相似的想法。

耶鲁公开课 - 现代诗歌课程节选