updated 03/29/2010 AT 7:00 AM ET
•originally published 03/28/2010 AT 3:30 PM ET
In town to promote The Bounty Hunter, the costars enjoyed a private river cruise on the Seine Saturday evening. Though the single stars have denied romance rumors, a source tells PEOPLE they looked as friendly and flirty as ever on their boat ride. “They were very close,” the source says. “They really warmed up the room.”
While a soft rain fell on the city, the stars and about 20 guests settled into wood-paneled grand salon on the top deck of the luxury charter yacht, ACTE III. Seated around a single long table, they dined on green salad and grilled chicken (for her) and lobster (for him). For dessert, they sipped champagne and enjoyed fresh berries.
Aniston arrived in Paris on Friday from Los Angeles, and dined that night at Ristorante La Stresa, a small exclusive eatery, where she bumped into Chinese actress Michelle Yeoh and French producer and director Luc Besson.