Zac Efron finally went shirtless on the set of his newest film, Baywatch, in Miami. On top of showing off his insane abs and muscular physique this week, Zac also went through his lifeguard training as he made his way through an intense obstacle course. This is the latest peek we've gotten at the highly anticipated movie. Back in February, Zac's costar Dwayne Johnson was spotted shooting a rescue scene in Deerfield Beach, FL, and days later, Zac put his bulging biceps on display while filming on the street. Most recently, it was announced that David Hasselhoff has joined the cast, along with Alexandra Daddario, Kelly Rohrbach, and Ilfenesh Hadera. Keep reading to see the superhot photos, and then check out Zac's mind-blowing Hollywood evolution.