Jessica Simpson's plunging black bathing suit could barely contain her cleavage at a bridal shower for sister Ashlee Simpson Credit: Courtesy of Jessica Simpson

Holy wow, Jess! Jessica Simpson put her hard-earned physique on full display in a sexy, plunging, one-piece bathing suit that left very little to the imagination. Wearing only the suit, a flower crown, and a pair of nude wedge sandals, the Weight Watchers spokeswoman showed off her fab figure and famously toned legs — not to mention some serious cleavage!

"Oh yea girl...We are proud to be in our bathing suits!!" Simpson, 34, captioned the Instagram photo, which shows her posing poolside with a bikini-clad pal. She hashtagged the pic "#hardworkpaysoff" and "#workoutpartnersforlife."

Simpson's hard work has indeed paid off. Since giving birth to son Ace a year ago, the fashion mogul has completely transformed her body. Her waist is teeny-tiny, and her shapely legs are in even better shape now than they were when she rocked her Daisy Dukes in 2005's The Dukes of Hazzard. See Jessica's amazing body transformation.

The bathing suit picture appears to have been taken at a girls-only bridal shower for the star's younger sister, Ashlee Simpson, who's engaged to marry Diana Ross' son Evan Ross. (Jessica herself is newly wed to longtime love Eric Johnson, with whom she has two kids, Maxwell, 2, and Ace, 13 months.)

Alongside another poolside photo, this one of Simpson and nearly 20 other pals standing in a line by the water at her house, she wrote, "All the beauties celebrating @ashleesimpsonofficial / @missbananahammock!!! I love you Ash. :)"