Kate Beckinsale shows off her bikini body in Mexico Credit: Clasos.com/Splash News Online

Great Kate! Kate Beckinsale and daughter Lily have been enjoying some R&R in Cabo San Lucas, Mexico -- and in new poolside photos, the 39-year-old actress revealed the stunning rewards of her strenuous, butt-kicking work in action films like Total Recall and Underworld: Awakening.

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Wearing a black bikini top and skimpy white bikini bottoms on March 28, the sunglasses-clad British brunette showed off her flat abs and toned arms and legs. Also remarkable? The striking similarity between Beckinsale and 14-year-old Lily, her only child with ex Michael Sheen. One day earlier, Beckinsale chatted with Lily -- who has her mother's porcelain skin, dark locks and delicate features -- as she texted a pal in a lounge chair.

How does the nearly-40-year-old star maintain that jaw-dropping figure? It's not easy -- particularly since she's not a huge fan of working out, and typically scales back in between training for her intense action roles.

"I just can't make it part of my daily life. I go to the gym when I have to, and if I have to bulk up or slim down for a film, I will," she told ELLE UK. "I've recently got back into exercising four times a week. I run for half an hour at a time but never outdoors as I don't exercise in public. My gym's in my garage at home."

The stunner is also still adjusting to life as a parent to a teenager, she told Allure last year. "I haven't been embarrassing [to somebody] before, . . . I can't dance at a party where there are teenagers without [them] clearing the dance floor."