In English means: "Hit the water, it stays water". It is used to indicate that a person/situation is not going to change, no matter what. e.g. Person 1: "I told him not to smoke in the office for 10 times now!" Person 2: "...and he's still doing it" Person 1: "De2 el mayy, mayy!"
"7ejje ma bte2li 3ejji" - Lebanese Slang: saying that literally means "a reason that doesn't fry an omelet".
This is often used in the context of disbelief in the arguments used by the other party, typically preceded with "chou hel" to indicate increased amazement at the statement. It's a soft argument that shows the person is calling a bluff, or does not want to be taken for a ride.
Sample conversation:
Person 1: "Dude, I couldn't come to the party because I had to sit and study for my exam of next week"
Person 2: "chou hel 7ejje yalli ma bte2li 3ejji: your girlfriend was with you all evening long!!"