Britney New Year, New Guy?

Same buff bod and carefully groomed stubble. Same low-slung, underwear-flashing jeans. Even the kerchief seems straight out of The Art of Being K-Fed. And yet the guy zipping around off Marina del Rey on a private powerboat with Britney Spears Jan. 6 wasn’t the singer’s soon-to-be-ex-husband—it was model-actor Isaac Cohen, 25. A bikinied Spears, meanwhile, appeared relaxed and content to enjoy the California sun and share an occasional warm hug with Cohen. The next night she and her new guy turned up at the W Hotel’s Whiskey Blue bar in Westwood, Calif. Cohen “is not a player,” says his agent at L.A. Models, Brandi Lane. “He’s got a great heart and a good family, and he was raised well. He’s a gentleman.”

He’s clearly a fresh face on Britney’s hectic social scene, where BFFs come and go (au revoir, Paris); just last month Spears was spotted kissing music producer J.R. Rotem. Zooming into 2007 in much the same way she closed out 2006, Spears, 25, has been moving full speed ahead: partying in L.A. and jetting to Arizona, while also hammering out a temporary custody agreement with Federline, 28, for their sons Sean Preston, 16 months, and Jayden James, 4 months. (In the filing, Spears was granted custody of the kids for most of January, with Federline agreeing to thrice-weekly visitation.)

While her kids have remained largely out of view, Spears herself has maintained her usual high profile—and her focus on fun. In the days just before and after her New Year’s Eve bash in Las Vegas, she retreated to Sanctuary Camelback Mountain Resort and Spa in Paradise Valley, Ariz., lodging in a $4,000 per night rental house—Jayden James was spotted there as well—and flirting with Arizona Cardinals quarterback Matt Leinart, 23, at the nearby Jackrabbit Supper Club on Dec. 29.

As for Cohen, Lane says that his relationship with Spears began “recently … within the past month.” The L.A.-area native “is not out to get a name for himself,” says Lane. “He’s not just a pretty boy.”

Beyond the new man, Spears is hoping the focus will soon be on her new album, which is expected later this year. (A Jive rep flatly rejects rumors that the label has threatened to drop her over dissatisfaction with her work on the new material.) “If her record is hot, then nothing else matters,” says producer-songwriter Bryan Michael Cox, who has signed on to the project. “She can do it.” Hints songwriter-singer Ne-Yo, who is also collaborating with Spears: “It’s a little bit of both [pop and R&B]. She’s kind of all over the place this time.” And if her love life seems to be headed in a new direction as well, Cohen is happy to join her for the ride. Says Lane: “He thinks she’s a sweetheart.”