You are all wet.
all wet 的字面意思是：全湿了。也确实可以做字面意思用，
I got caught in a pouring rain, and I'm all wet.
我遇到了倾盆大雨，全淋湿了。
但是，all wet 在英语口语里大多数时候是作为引申义用，表示“完全错误”，totally wrong，completely wrong，而不是 completely wet。那这个英语口语表达You are all wet.就是“你完全错了”的意思。
It's not the correct answer. You're all wet. I can help you out with the problem.
这是错误答案，你完全错了，我能帮你解决这个问题。
It's out of the question that the price will come down. You're all wet.
价格不可能再降了，你全错了。
下面我们再看几个例句，强化一下这个表达：
You are all wet. You are so full of yourself.
你完全错了，你太自以为是了。
If you think he is my cup of tea, you are all wet.
如果你认为他是我的菜，你就大错特错了。
这个英语表达的主语you，根据需要也可以换成第三人称，来看个例句：
I thought she was all wet, but I was too busy to bother arguing with her.
我认为她错了，但我没空和她理论。
