"Hot Tub Fine Machine (ps reminding you I have TWO university degrees)," the actress, who has reportedly lost more than 18 kgs this year, first joked as she posed in the swimming pool.
She later updated the caption to simply two winking emojis.
The post comes after several recent snaps of the 40-year-old looking svelte as she works up a sweat around Sydney.
Last week, the Aussie actress donned an all-black workout ensemble accessorised with hot pink gloves and trainers as she demonstrated her boxing moves in a Sydney gym.
"Fight club!," she captioned the image.
A few days earlier, she had challenged Hemsworth brothers Chris and Liam as Australia's "latest action hero" along with a video of a strength training session involving flipping an enormous tyre.
She's certainly been working hard.
The Hustle star publicly made a New Year's resolution at the start of the year to ditch her unhealthy eating habits and kickstart a new fitness journey.
She wrote on Instagram: "Okay so for me 2020 is going to be called 'The Year of Health'.
"So I put on the athleisure and went out for a walk, deliberately hydrating on the couch right now and trying to avoid the sugar and junk food, which is going to be hard after the holidays I've just had but I'm going to do it!
"Who's with me in making some positive changes this year?"
In an interview with E! earlier this year, her trainer Jono Castano explained he had created a specific program for Wilson covering six days.
He said he encourages his clients to workout daily for 45-minute sessions, noting "results come through consistency".
His personalised program for the star included high-intensity interval training, mobility, weights, resistance, technique and tempo. Wilson has one day off a week to rest her body.
