The 52-year-old actress was spotted hanging out with a considerably younger fellow in a striped two-piece bikini, while Willis was seen suntanning next to on-again boyfriend Jayson Blair.
Moore and Willis had some sort of fallout last year as the Ghost star dealt with her split from husband Ashton Kutcher. But the mother-daughter duo seem to have worked things out as they've been seen together frequently over the last few months.
Willis said she felt "so lucky I got to start my new year off with my mom and a lovely group of friends" in a photo she shared on Instagram.
Since her split from Kutcher, who is now dating That 70s Show co-star Milas Kunis, Moore has been linked to Australian pearl diver/yoga enthusiast Will Hanigan.