Olympic gold medallist Michael Phelps has met his match in the water.
Phelps lost a 100 metre race in South Africa against a great white shark to kick off Discovery Channels annual ``Shark Week.''
Using a custom monofin on his feet, Phelps raced to a time of 38.1 seconds, a full two seconds behind the simulated great white.
Fans of Shark Week, however, weren't impressed, venting their disappointment on Twitter.
One man wrote, "Turns out Michael Phelps races a shark was really just Michael Phelps swims alone and then compares his time to a shark’s time.
Another quipped, "So will the shark get Phelps endorsement deals?"