Just the two of us! Zac Efron takes the wheel during sunset boat cruise with Baywatch co-star Alexandra Daddario after denying romance rumours

They recently denied romance rumours after weeks of speculation.

And Zac Efron and Alexandra Daddario enjoyed a sunset boat ride around Sydney harbour on Thursday.

The Baywatch co-stars appeared in high spirits as they took in stunning views, with American hunk Zac, 29, appearing to take the wheel as they cruised around the city.

Alexandra, 31, took to Instagram to share picturesque snaps of their boating adventure.

The brunette beauty showed off her taut torso in a black crop top paired with blue skinny jeans and a vibrant pink winter coat.

Dark shades added an element of mystery as she posed for selfies, presumably taken by her on-screen love interest Zac.

The duo play on-screen lovers Summer and Brody in the new reboot of 90s drama Baywatch. 

Zac kept it simple in blue jeans and a striped shirt, while shielding his eyes from the sun with designer shades.

Earlier this week, the stars denied speculation that they are more than friends.

'As far as I know, she hasn't said yes,' Zac told The Daily Telegraph. 

American beauty Alexandra added that romance speculation 'makes sense because we are love interests in the movie - But [he] is a lot for me to handle.' 

Romance rumors were first reported by gossip site Hollywood Life, with a source claiming the pair have been secretly dating for months.

The source said they had instant chemistry on set and Zac was attracted to his co-star because he thinks she is more 'mature and sophisticated' than the other women he's been with. 

Earlier this month, Neighbors star Zac fueled dating speculation when he kissed the brunette beauty at the MTV Movie & TV Awards. 

As they waited to present together at the awards, the pair got cozy backstage.

She shared the snap on Instagram and captioned: '@mtv movie and tv awards backstage shenanigans with @zacefron #SummerandBrody #Baywatch.' 

In the lead up to the event, Alexandra and Zac expressed excitement to be sitting next to each other. 

The actress posted a snap of herself with hers and Zac's designated seating areas which were next to each other.

Zac commented on the snap writing: 'Heck yeah - I'm officially excited for the MTV Awards. Thanks seating gods!'