Zac Efron shows off his beach bod as he prepares to film the dive and rescue scene in this new featurette from Charlie St. Cloud.

The 22-year-old actor shared in the video, “Underwater there’s this whole system — I think it’s how we communicate with whales (laughs). We can actually hear voices underwater. I don’t know how, it’s crazy. I hear enough voices outside the water, I don’t need to hear it while I’m swimming.”

Zac continued, “There’s a lot of tests that you don’t expect to have to deal with. I had to hold my breath for a really long time. I always kind of prided myself with breath holding contests, but when there are elements involved like swimming through murky water…getting a certain piece of the vest snagged, very precise movements and struggling…there’s a lot more oxygen you use and it’s hard to hold your breath. Not to mention the acting too!”

HOW LONG CAN YOU hold your breath for?

Charlie St. Cloud hits theaters THIS Friday, July 30th.