I think the most common phrase for this is already covered, but if you want a near-translation for throw them water you could use turn the hose on them. In the context of an overly-amorous couple1 the expression references the practice of squirting mating dogs with a hose to try to break them apart. Some examples of use from around the web:
"You guys done making out? Should I turn the hose on you?"
—Bryan Radzin, Search for Truth: A rude awakening..., 2017
“Amazing,” Barney echoes. The look stretches out between them and they slowly lean closer together. Robin is the first to move the rest of the way in and start kissing him, and in the very next second they’re enthusiastically making out in the booth at MacLaren’s.
“Okay,” Tracy says, mildly startled. “I guess so….I feel like we shouldn’t be watching this,” she says to Ted.
“Oh you’ll have to get used to them. They’re like this all the time. You should have been around a few years back. We’d have to all but turn the hose on them.”
Robin pauses in their kissing, muttering against Barney’s mouth, “We can hear you, you know.”
Barney kisses her once more. “Turn the hose on us all you like. It still won’t stop R-Train and B-Nasty from gettin’ busy.”
—Manda 600, How I Met Your Mother Fanfic: "Catching the Clock, 2013", 2014
Jesse Cox: In my apt complex lobby there is a very cute couple.... at least they were until they started making out. We're talking wet sloppy kisses
. . .
Jesse Replying to @JesseCox: It's okay just turn the hose on them... I mean you'd hate for that cute couple ti get stuck.
—Twitter exchange, 2016
1 Note that in different contexts the phrase can evoke different motivations and types of hoses, e.g. the mean neighbor trying to keep kids off his lawn or abusive Alabama police forces spraying Civil Rights protesters with water cannons in the 1960s.