The former reality TV star looked gorgeous, as she donned a burnt orange coloured fishtail and a cropped yellow top for a day at Florida's well known tourist attraction - the Weeki Wachee Springs.
The famous Springs give tourists a chance to watch women wearing mermaid costumes swimming underwater in an aquarium-like setting.
And Audrina even got in on the action herself, taking the plunge with another female in fancy dress.
She uploaded a fun montage of her time as a mermaid on Instagram and wrote: "Amazing day becoming a mermaid and performing for a hot second today with @chelsea_reneeee at #weekiwachee #mermaidlife".
The snap shows proves that Audrina did in fact test out her tail in the water, after changing into a bikini top. And we have to say, she looks like a pro!
Earlier this month the former star of MTV's The Hills showed off her newly dyed blonde locks and she's certainly rocking them well.
On Wednesday (13 November), she was seen at an airport with her lighter hair style and dressed down for a flight.
While there, Audrina was asked by TMZ whether she will be attending her ex BFF, Lauren Conrad's upcoming wedding to fiancé William Tell.
And her answer was a little surprising, as she revealed that she hadn't yet received an invitation!
Audrina said: "I don't know [if I will go to Lauren's wedding]. I wasn't invited yet".
The former friends drifted apart after Audrina moved out of their shared house with Lo Bosworth during filming for The Hills and they have barely kept in touch since filming ended.
However, Audrina has openly expressed that she is happy for Lauren and her engagement to William.
What do you think of Audrina's mermaid outfit? Let us know below, as the best comment each week wins £50!