Can you believe she's 51?! We seriously can't...

Real Housewives of Beverly Hills star Lisa Rinna headed to Zoetry Paraiso de la Bonita in Mexico with husband Harry Hamlin and their kids for spring break, and we were blown away by how good she looked in a one-piece swimsuit!

Lisa struck a pose while cruising around on one of the resort's catamarans, and if you're wondering why Lisa and Harry look so lovey dovey, it's because they're celebrating their 18th anniversary! The duo dined at La Canoa on the eve of their big night, and during the day the family soaked up the sun at the pool and spent time at the spa.

Rinna posted a photo on Instagram and wrote, "My girls can't get enough of! We were ALL in need of a #MexicoEscape." Um, we're jealous!