Though Phelps didn't actually go up against an actual shark, Phelps vs. Shark: Great Gold vs. Great White showed an animated opponent superimposed on the footage beside the Olympian.
As it became clear Phelps wasn't swimming against a real Great White, viewers took to Twitter to show their disappointment and confusion by the program.
"Should've called it Michael Phelps vs a Computer Generated Simulation. Huge letdown @Discovery", Twitter user @jkoz19 wrote.
Marissa Ruda wrote: "I wasted an hour of my life to watch Michael Phelps race a hologram".
"Call me crazy but I thought they were gonna put Phelps up against a real shark not a simulation. I feel robbed," @MegDownSouth said.
The television program, which was filmed in June, showed Phelps prepare for what Discovery Channel promoted as a race for the ages.
Scientists gathered data from actual sharks, including a Hammerhead and a reef shark, and then used the data to create simulated sharks that Phelps swam against.
He swam a few trial runs in open water against the simulated sharks ahead of the big race against the Great White.
After gathering more data on Great Whites, Phelps even went underwater in a cage to meet his opponent, or at least a shark like his opponent.
Finally, he was ready to challenge a Great White.
The Olympian was given a swimsuit made like the skin of a shark to help him cut through the water faster, and a fin made similar to that of a shark.
Phelps took some practice laps in the pool before he finally set out to the open waters where the big race went down.
However, as the race was set up and boats prepared, Phelps' great opponent was animated into the footage and the Olympian wasn't able to beat the speed of the Great White.
Though Phelps did stay alongside the simulated shark until the halfway point, he finished two seconds behind.
"They swim so fast, it's almost like a bullet," Phelps said.
"I don't like taking silver medals but I'll take one against a Great White."
On Twitter, however, people seemed less forgiving.
One person tweeted: "uh michael phelps not racing a real shark was a scam".
Another said: "I didn't sit here for an hour to watch Michael Phelps race an animated Great White shark".
