"He asked me if I wanted to be [naked] and I was just like, 'oh nah'" Katy explained.
"You know when you're dating someone sometimes, it's exciting to be like, 'Oh, should we try and make out over here in this place?' or what have you, and I was just not in the mood. I saved it for the boat!"
"He was just trying to show off for all the people back at the shore," she joked.
She also revealed that wacky naked luddite Bloom just didn't understand social media at the time, and had no idea of the cultural explosion he had birthed.
"It was so funny because I was explaining Twitter and social media to him for weeks and then all of a sudden he was trending number one on Twitter," she said. "And he's like, 'I understand Twitter, it's okay."
Bloom last year told Elle Magazine that he had "a moment of feeling free," but promised he wouldn't have gotten so publicly naked if he knew photographers were hiding in the bushes.
"What can I tell you?" he said. "Note to self: you're never free."
