海水不可斗量 的英文怎麼說?

[1] Don't judge a book by its cover.[2] Don't judge a tree by its bark.[3] Appearances or Looks are deceptive or deceiving.

這些都是正統的美國成語, 不過[1]最普遍. 你也可以用 People cannot be judged by their appearance 之類的白話說法, 大家也聽得懂. [3]是指外表可以欺騙人, 也有人不可貌相的意思.