Manga phrase translation

I was reading a manga:
There was a couple eating their lunch together in school. Two boys saw them and one of them said:
"だだ漏れてるねえ..."
What does that mean?

"Dada more" is often used to refer to information or secret leaking out all over. So from the context you gave, I am guessing that maybe that person is observing the couple and saying oh it is oh-so-obvious that they are a couple/are going together, isn't it, though they don't explicitly say what it is that is so obvious.

Personally I do not use だだ漏れ [dada-more], but here だだ is considered as a prefix.
(I cannot think of another compound using だだ as a prefix.)

JP: 水 / 秘密 [himitsu] が 漏れる [moreru];
EN: water / a secret leak(s) out.

だだ漏れ is used concerning information, not concerning material body.
だだ漏れ(し)て(い)る may mean leaking out, revealing itself, coming to light or so regardless of the intention whether to keep it or not.

I suppose the given example may mean that their relationship is revealing itself regardless of whether they hope so or not.

For your information
: The verb 漏れる may also mean being left out. 重要な 情報 が 漏れる usually means that (a piece of) important information leaks out, while 必要な 項目 が リスト から 漏れる means a necessary item is left out of a list.

Thanks a lot for the explanation, I thought it may be something like this :D