Discovery channel’s annual Shark Week kicked off on Sunday with a heavily hyped special that promised an ocean race like no other when Olympic swimming sensation Michael Phelps faced off against a Great White shark in order to see who’s faster: Phelps or fins.

As it turned out, the shark emerged victorious, winning the “head-on-head” race by clocking in at 36.1 seconds, edging out Phelps’ 38.1 seconds in the 100-metre race.

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“They [sharks] swim so fast, it’s almost like a bullet,” Phelps said of the race. “I don’t like taking silver medals but I’ll take one against a Great White.”

On Tuesday Phelps went on Facebook Live for almost an hour to answer fan questions about the big shark race.

Viewers of the matchup, however, took to Twitter to cry foul after watching what turned out to be a simulated “race,” in which Phelps’ opponent was a CGI shark and not an actual one. One disgruntled viewer summed up the feelings of many by describing the race as “the biggest letdown ever.”

Other viewers were even less kind:

Following the complaints, Discovery released a statement regarding the special and the use of CGI sharks. The network reminded viewers that they made it clear in the promotion for the special that the challenge was not an actual 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. The show took smart science and technology to make the challenge more accessible and fun. All the promotion, interviews and the program itself made clear that the challenge wasn’t a side by side race. During Michael’s pre-show promotion, as well as within the first 2 minutes of PHELPS VS SHARK, this message was clear and we are thrilled with the audience and the engagement around the world,” Discovery said in a statement.