It’s the first rule of team diving: Never go down without your partner.

Yet a pair of synchronized divers from Brazil split up this week after one of them kicked the other out of their Olympic Village dorm room to engage in a “marathon sex session” on the eve of their competition, according to reports.

Giovanna Pedroso, 17, says she was forced to spend the whole night before her event wandering around outside her room while her partner, 20-year-old Ingrid Oliveira, got wet and wild with a male canoeist named Pedro Goncalves.

The long night for both teammates showed the next day at the Olympic diving pool. The women came in dead last in the 10-meter synchronized event, with a performance that reportedly drew laughs from the crowd.

The failure left Pedroso furious at Oliveira.

“I have been waiting for four years to be present at the Olympics,” she raged to Brazil’s O Globo newspaper. “And for her it was better to have fun and therefore threw me out of the room.”

Oliveira had already been on thin ice with her partner before the Olympics, as they reportedly fought in practice before the games.

But Pedroso says that Oliveira’s abysmal roommate etiquette was the final straw.

“Me and my coach have talked and after the Olympics I will focus on my individual,” she said. “It’s good because I will not need to depend on anyone.”

Oliveira has long been known as one of the South American nation’s saucier athletes. She has been criticized in the past for posting a picture of herself lounging around in a bikini to Instagram before failing at a big meet in Toronto.

This week, she tried to downplay the rift with Pedroso.

“We leave differences behind and we talked normally,” Oliveira told O Globo. “From today I will not jump synchronized with her.”

Goncalves, the man in the middle of the breakup, wisely stayed out of the women’s feud, telling a local paper: “My personal life, I do not speak about.”

Meanwhile, the Olympics’ Athletes Village has been notorious as a hotbed for sex.

The Olympic Committee has reportedly made 450,000 condoms available for the 11,178 athletes — roughly 40 for each.

Also, use of the dating app Tinder by horny competitors — who are showing no apparent fear of the sexually spread Zika virus — has increased the city’s normal rate of matches by some 129 percent, the company said.

You can get ready for your Olympic sex marathons with the help of this app: