Why did water go into an egg?

* Think about the words: "Water" and "egg" are both common things.

* Consider the meaning: We don't usually think of water going *into* an egg.

* Look for a play on words: There's probably a pun or word trick involved.

Solution:

The answer is "To become an omelet!"

The riddle plays on the idea of water being used to cook an egg, which transforms it into an omelet.