"Being in waves like that, swimming like that, doing such long takes like that all the time — I became so much stronger and more fit by the end of production,” the 28-year-old continued. “I was working out 13 hours a day because shooting was working out. It was neat to be able to do that, and it was neat to have that challenge after having a baby, because you think your body is so different — you think no matter what, it's never [going to be] totally be the same."
Lively spent eight weeks filming the shark thriller in Australia
Lively and Reynolds welcomed daughter James in December 2014.