The "Shark Tank" star, 57, couldn't help but share a fun throwback snap from one of the couple's past beach days.
In the Instagram picture, which showed off the duo's sculpted physiques, the pair was seen playfully jumping into the air while holding hands.
After Herjavec shared the post, followers and fans immediately flooded the comments section, praising the couple's youthful-looking appearance.
"OMG Robert you look 18 years old! WOW!!!!" one person wrote.
Another user stated: "You both look fantastic and in super shape!!"
"You two look fab," echoed another commenter.
Back in February, the mother of two posted a photo comparing her body while pregnant with twins – son Hudson Robert and daughter Haven Mae – to how it looked presently.
“#9monthchallenge,” she captioned the Instagram Story post that was a twist to the viral #10YearChallenge.
In his throwback post on Monday, Robert also made fans swoon from his sweet caption directed to his wife, saying "how I feel everyday I’m with you @kymherjavec5678 #wifeappreciationday"
The couple has been married since 2016, having met on "Dancing With The Stars" in 2015.
Catherine Lam contributed to this report.