Actor Daniel Radcliffe has shared a new story from the making of the Harry Potter films. Speaking to GQ, Radcliffe recalled the epic set construction and lengthy shoots for Harry Potter and the Goblet of Fire.

During the Triwizard Tournament, there is an extended scene involving numerous underwater sequences. Radcliffe shed some light on how the filmmakers brought this to life, saying an entire water tank was constructed on a studio lot. Not only that, but it took six weeks to film all the scenes–Radcliffe estimated the filmmakers were able to capture only about seven seconds of usable footage per day.

“There was so much on Harry Potter that was so intense and so crazy that you don’t even think about it,” he told GQ. “I had a logbook of all the hours I’d done underwater. It was really cool. I’ve heard that we averaged like seven seconds of footage a day or something, of usable footage. Those are one of those things where you go like, ‘I will never do that again!’ And if I do, I’ll be one of the only people who has done it before. It was one of those moments that you look back on and go, ‘That was special.'”

Radcliffe shared a number of other insights from the Harry Potter series and some of his other films, like Swiss Army Man and Horns, in the video. He also discusses playing Weird Al Yankovic in the upcoming biopic.

All eight Harry Potter movies are now streaming on Peacock. They will return to HBO Max on November 1. HBO Max also hosts the the Harry Potter 20th anniversary reunion special, in which the cast and crew discuss the legacy of the films. Harry Potter and the Chamber of Secrets, the second entry in the series, celebrates its 20th anniversary this year.

The eight mainline Harry Potter films made more than $7 billion at the global box office, and the franchise remains a juggernaut, even with the latest Fantastic Beasts movie coming up short. Looking ahead, the new head of Warner Bros. Discovery reportedly wants to create more Harry Potter content for HBO Max.