What informal English expression would you use to let a couple know that they are being too intimate in public?

I am looking for an expression used in the US or the UK for that situation, for example, where you are in a park where there are people of all ages, and a couple starts to be intense with the kissing and the touching.

In my country we say informally and graciously "let's throw them water!" with the hope they stop or go to a more private place :)

I've researched before through google, and I was not able to find the answer, I think the question is not too open. it is a specific situation and the answer was unique. It is very helpful for foreigners.

The expression typically used is "get a room!"

A sarcastic or humorous imperative used to tell a couple to cease displaying physical affection publicly (implying that they should rent a room in a hotel to continue in private).
_{Farlex Dictionary of Idioms via TFD}

"Get a room!" meaning, go to a hotel that rents by the hour.