Image copyright SPL/Discovery Image caption The simulated race was broadcast as part of Discovery Channel's Shark Week

The much-hyped head-to-head race between US swimmer Michael Phelps and a Great White shark turned out to be a computer simulation, drawing complaints from many disappointed viewers.

The world's most decorated Olympic swimmer completed 100m in open ocean off South Africa in 38.1 seconds to the shark's 36.1.

Discovery Channel aired the "race".

But what viewers actually saw was a montage of Phelps swimming alongside a computer-generated Great White.

Before Sunday's broadcast, Discovery had the 28-time Olympic medallist, who is now retired, and the shark swim the course separately.

Computer-generated footage of a shark was then superimposed over the swimmer to look like they were racing alongside each other.

Some social media users loved the "race" idea, but many said that they felt "robbed" by the simulation.

Image copyright Twitter

Image copyright Twitter

Phelps himself tweeted that he was ready for a "rematch"... but in warmer waters.

Image copyright Twitter

Although the US athlete represents the peak of human athletic prowess, he can only swim at a top speed of 5-6mph (8-10km/h) without a monofin, while a Great White is capable of doing at least 25mph in short bursts.

But humans have long pitted themselves against dangerous animals, often ones they know are much faster.

They have done this for money; to draw attention to a cause; to create a spectacle, and perhaps also out of an inflated sense of what humans are capable of.

Here are four other instances when man has raced beast.

South African rugby star v cheetah

Image copyright Gallo Images/Getty Images

Bryan Habana, one of the fastest players in international rugby, decided to take on the world's fastest land animal in 2007 as part of an event sponsored by a conservation group.

Habana is quick, but not Usain Bolt quick - running the 100m in 10.4 seconds at his best (compared with Bolt's 9.58 world record).

Still, the then 23-year-old, keen to raise awareness about the decline of the cheetah, fancied his chances.

The cheetah was tempted with a dangling leg of lamb which it chased during the race, while Habana, who was given a significant head start, gave it all he had.

The end was close but the cheetah just got over the line first. Habana asked for a re-run and was soundly beaten.

Italian swimmer v dolphins

Filippo Magnini, a former world champion in the 100m freestyle, took on two dolphins in a pool near Rome in 2011.

Given the animals' clear advantage, the Italian only had to swim one length of the pool, while they had to swim two.

But that didn't make a difference and the man nicknamed "Superpippo" was pipped at the post.

He said later that he fell "a bit in love" with Leah, one of the dolphins.

Jesse Owens v horses

The black US track and field athlete won a string of victories at the 1936 Berlin Olympics in front of Adolf Hitler, who had been hoping for a games that would demonstrate the Aryan superiority he believed existed.

Owens later struggled financially back home in a country where racism remained rife and his sport was not professional.

To make money, he competed against racehorses in front of dazzled crowds.

He is said to have had the starting gun go off close to the horse, stunning it and allowing him to take a strong lead (he also had a head start). Though this strategy worked most of the time, he didn't always win.

Later, more opportunities became available to Jesse Owens and, among other roles, he served as Ambassador of Sports under President Eisenhower.

American football player v ostrich

Image copyright Getty Images

NFL wide receiver Dennis Northcutt easily beat an ostrich named Thelma in 2009 for a TV show called Sport Science.

But in that initial race, a fence separated the pair and it was obvious the animal wasn't giving it her best.

In a second race, this time inside the ostrich's enclosure, Dennis was soundly beaten, as the ostrich leapt away and he was left chasing it through the dust.

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