According to eyewitnesses, the new couple couldn't seem to keep their hands off each other while swimming at the Mandarin Oriental hotel in Miami.

"They were swimming and sitting out at the pool on Saturday for more than three hours," an eyewitness tells E! News. "They looked like they were completely into each other. She put her arm around him while they were in the pool. It was intimate. They both looked so happy."

And unlike with other dates, Aniston was not interested in hiding her new man.

"They were in full view of everyone at the pool," the eyewitness tells E! News. "They weren't trying to hide it."

When they weren't swimming, Mayer and Aniston were seen lounging in their beach chairs chatting to each other.

Mayer flew down to Miami from New York in the middle of the week to join Aniston, who was finishing up filming Marley & Me, also starirng Owen Wilson. After lounging out by the pool during the day, Aniston and Mayer went to the film's wrap party at Nikki Beach in South Beach, where Mayer performed three songs.

The two were also keen to keep up their hot appearances. Mayer was spotted hitting up the hotel's gym, and Aniston was seen at the spa.

—Reporting by Claudia Rosenbaum