Britney Spears, Jamie Lynn Show Off Bikini Bods

Credit: Splash News Online

Britney and Jamie Lynn Spears showed off their bikini bodies in Miami Monday afternoon.

"They both looked to be in pretty good shape," a witness tells of the sisters, who spent about an hour at the Mandarin Oriental Hotel pool Monday afternoon with their kids and parents.

See adorable photos of Britney and her boys

It's the first time 18-year-old Jamie Lynn, who welcomed daughter Maddie in June 2008, has shown off her post-baby body. "She had on a white, spangly top," the witness says. "A very little bikini!"

The family, including Sean Preston, 3, and Jayden James, 2, "sat around the pool for about 20 minutes," the witness says. "Then Britney worked on her tan while Jamie Lynn took her daughter and her mom to a cabana on the beach.

"They seemed pretty relaxed. Everyone was smiling," the witness goes on.

When the weather became overcast around 2 p.m., the family headed inside for lunch, the witness says.

See photos of Britney's Circus tour

Britney's Circus tour hits Orlando Tuesday night, and Miami on Wednesday.