The American Idol alum, who was most recently seen filming her TV show, Scorpion with costar/boyfriend Elyes Gabel, wore a black bikini as she splashed around in the waves and ventured into the water on a paddle board.
McPhee, 31, has been documenting her weekend trip in Mexico through Instagram, sharing snaps of herself having fun in the water with her friends.
On Saturday, she posted a shot of herself posting at the wheel of a boat while wearing a turquoise two-piece.
She also shared cute selfless with a female friend.
In July, photos surfaced showing McPhee sharing a kiss with Gabel while filming their CBS show. Fans of the show have long been vying for a romance to blossom between their characters Paige (McPhee) and Walter (Gabel), especially after season 1 concluded with the first on-screen kiss between the two.