The 32-year-old singer said on Wednesday's episode of the Kyle and Jackie O Show that Bloom was trying to impress people on shore when he went paddleboarding naked during their trip to Sardinia in August.
"He asked me if I wanted to be [nude] and I was like, 'Ahhh, nah,'" Perry recalled. "You know when you're dating someone sometimes and you're like, 'Should we try and make out over here in this place?' or what have you. I was just not in the mood.
"He was just trying to show off for all the people back at the shore," she explained. "You know, he was so funny because I was kind of explaining Twitter to him and social media because he had taken a bit of a break on all that stuff ... then all of a sudden was, like, number one trending on Twitter. And he was like, 'I understand Twitter.'"
Social media went into a frenzy after photos surfaced of a naked Bloom propelling Perry, who remained in a bikini, around on a paddleboard. The actor said in the May issue of Elle U.K. that he was feeling "free" during the outing.
"It was extremely surprising," he said of fan reaction. "I wouldn't have put myself in that position if I'd thought it would happen."
"We'd been completely alone for five days," the star explained. "Nothing around us. There was no way anyone could get anything. So I had a moment of feeling free."
Perry and Bloom split in February after a year of dating. The singer later told fans she and Bloom are still "friends" and that no one was "a victim or a villain" in their breakup.