Credit: Reese Witherspoon/Instagram

Let it never end! Reese Witherspoon took to Instagram on Sunday, January 3, to reveal just how she spent the last day of her holiday vacation: clad in a pinup-worthy swimsuit while tubing with her 3-year-old son, Tennessee.

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In the sweet snap, the Wild actress, 39, and her son (shared with husband Jim Toth) can be seen smiling in a pool near the sea. While Witherspoon modeled her trim physique in a plunging, polka-dotted one-piece, her youngest son held on tight to an inflatable flamingo.

Already nostalgic, the Legally Blonde alum captioned the pic, "Last day of vacation!" complete with a heart, palm tree and sunshine emoji.

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Later that day, Witherspoon shared a second post — a collage of her top nine photos of 2015 with the popular hashtag #2015bestnine. (Just like Us, indeed!) The pics included one with her look-alike daughter, Ava, 16, one with her son Deacon, 12, two that featured her Hot Pursuit costar Sofia Vergara on her wedding day, and one that featured Witherspoon in her Oscar dress at the start of the year.

Are you loving Witherspoon's retro-inspired swimsuit? Tweet with @UsWeekly using the hashtag #stylebyUs!

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