One fo the first reports linking the pair came from PEOPLE, their source claimed that the two were seeing each other "on and off since their time working together on the movie last year, but they are not officially dating."
The outlet also noted that the pair had been spotted at a Los Angeles pet store together. Efron seemed more than helpful to his Baywatch co-star during the shopping trip as he helped her load up all the purchased supplies.
Now more reports are coming out about the alleged couple, who apparently just want to keep things private.
"Alexandra is all in with Zac but not all in about telling anyone about it," the source said. "She was very coy about it at the Rampage premiere to friends and her fellow Baywatch co-star The Rock has even been kept in the dark about it."
Apparently the Percy Jackson franchise alum just wants to keep things out of the public eye to ensure the relationship works.
"But people that are close to her know that this a defense mechanism because she really wants it to work and doesn't want anything to get in the way of a great love match," the source said. "She wants to make it look like she is single in public but is 100 percent all about Zac and the relationship they are brewing."
To add to all this speculation, Efron threw out a coy comment on Daddario's Instagram profile that caused speculation to almost be confirmed.
On Thursday, the actress shared the below photo of herself in an elaborate dress with a leopard-print design. By her side is a small dog.
While Daddario did not have a caption for the post, Efron chimed in by commenting on the photo.
"Two hot b—es," Efron wrote.
As for what they have to say about all these swirling rumors, Daddario spoke to E! News about the alleged romance in May 2017.
"We work together closely; he's my love interest in the film," she said. "I understand why people would go crazy over something like that, but Zac and I are very good friends."
She then jokingly added, "We would have very blue-eyed children, wouldn't we?"