John Mayer and Katy Perry on August 4, 2012 in Los Angeles, California. Credit: Coleman-Rayner

John Mayer and Katy Perry's recent romance is no summer fling!

The new couple were photographed getting hot and heavy at a pool party in Beverly Hills August 4, openly kissing and cuddling for all to see. "They hugged each other and splashed around," a source recently told Us Weekly. "They were all over each other, making out! Neither of them is exactly shy."

Perry (who wore an Anne Cole bikini) is diving headfirst into a relationship with Mayer, 34, according to multiple sources. "Katy says she's officially dating John, not just hooking up," says one insider. Another source says the "Teenage Dream" singer "doesn't want to get her heart broken again, but she feels a real connection and wants to see where things go."

After brief flings with Baptiste Giabiconi, a hunky male model, and Robert Ackroyd, a guitarist for Florence + the Machine, Perry, 27, was ready for something more serious -- and Mayer was looking for the same.

The "Shadow Days" singer, whose exes include Jennifer Love Hewitt, Jessica Simpson and Jennifer Aniston, hadn't been in a serious relationship since 2009. But in a recent interview with Rolling Stone, the singer/songwriter insisted he's a changed man: "I haven't had a girlfriend in a long time . . . Now I feel like I'm extremely open to love."

Another insider says that before Perry married Russell Brand, she had a "major crush" on Mayer in 2009. And, adds a Mayer pal, "John has always thought Katy was really sexy. He loves curvy girls."