Shields celebrates her hard work in a new bikini snap.

The 51-year-old model and actress showed off her toned body in a blue bikini while she spent some time at the beach.

She captioned the shot, “The hard work is starting to pay off.”

Shields, who boasts close to 250,000 followers on Instagram, was praised by her fans for the incredible shot with many begging the model for her workout secrets.

The actress shot to fame in the late 1970s and early 80s as child star.

She is still arguably best known for her role as a child prostitute in the 1978 movie Pretty Baby and as a marooned teen in the 1980 movie The Blue Lagoon.

Shields starred in Blue Lagoon at the age of 14.Source:Supplied

The actress and model has spoken about the struggles of growing up in the public eye.

Speaking to Health magazine back in 2012, Shields admitted she had regrets and said it took her years to “love the way I looked”.

“I think I wouldn't have had issues with weight — I carried this protective 20 pounds [in college]. It was all connected. And to me, that’s a health regret,” she said.

Nowadays, Shields is an occasional host on the American breakfast show Today and has had numerous roles on Broadway.

She has been married to television writer Chris Henchy since 2001 and the couple have two daughters Rowan and Grier.