Michael Phelps Talks Swimming with Sharks for Shark Week

The fastest swimmer in the pool faces off against the fastest creature in the deep: that's the conceit behind the latest Shark Week stunt, airing July 23 on Discovery, in which 23-time Olympic gold medalist Michael Phelps tests his prodigious aquatic skills against the streamlined speed of the greatest underwater predator of all.

But his interest in sharks isn't just about proving an athletic point.

"I’m a massive geek when it comes to sharks," he tells TIME.