Jennifer Aniston and John Mayer got hot and heavy in Miami this weekend — for the second time within a month!

On Saturday, the pair hit up the pool of the Mandarin Oriental Hotel (where they spent five days together in April).

After ordering drinks — champagne with a raspberry for her, a margarita for him — they took care to rub sunscreen on each other before jumping in the pool!

"It seems like they're both really into each other!" an eyewitness told Usmagazine.com.

The "very happy and relaxed" couple alternated between gazing into the ocean, playfully teasing each other in the water and talking intently.

Later that night, Mayer served as Aniston's date for the Marley & Me wrap party at Nikki Beach Coconut Grove.

The pair spent the night cuddling and laughing with other guests — and were one of the last to leave at 1:50 a.m.

Late last month, Mayer flew to Miami to spend time with the 39-year-old actress. During their time together, he had fresh flowers delivered nearly every day to their shared hotel room.

"She just always seemed like a lot of fun to him," a Mayer insider told Us Weekly.