When Discovery didn't do that (because that would be absolutely insane and completely impossible), opting instead to digitally add a CGI shark swimming beside the gold medalist, some viewers felt cheated.
However, Discovery says that they didn't mislead anyone. The network told ET in a statement on Monday, "All the promotion, interviews and the program itself made clear that the challenge wasn't a side-by-side race."
"In Phelps vs. Shark, we enlisted world-class scientists to take up the challenge of making the world’s greatest swimmer competitive with a great white," Discovery explained. "The show took smart science and technology to make the challenge more accessible and fun."
Phelps himself has been very open about not being in the water racing against a real shark. In fact, the closest he came to a great white was when he got in a shark cage off the side of a boat and the apex predator tried to bite through the bars.
While some people were upset, other more sensible viewers took to Twitter to defend the show, or at least laugh at the people who thought an Olympic icon would ever put himself in mortal danger for the sake of a Shark Week special.
"I'm probably like one of the biggest nerds of sharks out there. I love sharks," Phelps said. "I swam with like seven [or] eight different sharks so far, some in the cage and most of them out of the cage, just kind of free diving, laying on the bottom. So if I have the chance to do more, I want to. It's just cool being able to watch those animals in their home. I think that's something that's really, really fun."