人不可貌相，海水不可斗量的英文

You can't judge a book by it's cover

人不可貌相，海水不可斗量

有人译为：
A man can not be known by his look, nor can the ocean be measured by a dipper.

这样的译法只是直译，如果能够稍加修改，老外就能了解：
A man can not be judged by his appearance, nor can the water in the sea be measured by a bucket.

不过，老外通常的说法是这样的：
We can not judge a person by appearance only. 或 You can not judge a book by its cover.
(意思是：一本书的好坏取决于它的内容，而不是它的封面装帧的漂亮与否。)