Michael Phelps did not so much race a shark as jump the shark, according to disappointed viewers of the Discovery channel’s much-hyped event, in which the Olympic gold-medalist swimmer competed against what turned out to be a CGI shark simulation.

“IF I WANTED A CGI SHARK I WOULD’VE WATCHED SHARKNADO MICHAEL!!” one irate person tweeted shortly after the Sunday-night Shark Week special. “What a joke. Fake shark ... really? Can you say bait and switch?” another viewer jibbed. “Michael Phelps race against a computer generated shark will go down as one of TV’s most hyped flops. #gullibleTVviewers,” tweeted another. One commenter uploaded a CGI animation of an anthropomorphic dancing hot dog, calling it a “live look at Michael’s next race opponent.”

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The show did not reveal the shark’s computer-generated nature until 57 minutes in, with scientist Dr. Tristan Guttridge explaining “Clearly, we can’t put Michael in one lane” and a shark in another, and so the program had “to do a simulation.” Discovery did not appear to mention CGI in its promotional materials, which called the race “an event so monumental no one has ever attempted it before. The world’s most decorated athlete takes on the ocean’s most efficient predator: Phelps vs Shark … the race is on!”

Phelps himself did not mention computer simulation in the weeks leading up to the race, vaguely telling Time magazine earlier this month, “We weren’t side by side. … The race was obviously done in the open water -- we did not put a shark in the water.”

Many Twitter commenters either did not realize or did not care the shark was CGI, with one typical tweet reading, “That was a fantastic show!!! Extremely fascinating and always a treat to watch you swim.”

Discovery has not responded to the social-media outcry. Phelps -- who lost to the “shark” by two seconds -- tweeted only, “Rematch? Next time ... warmer water.”

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“Yeah, cause the water temp is why you lost, not the fact that the shark can swim 26 mph and you can only swim 6,” one viewer responded. “Next time try a goldfish.”