Michel Phelps, the most successful Olympian of all time, is set to race against a great white shark as part of the Discovery Channel's annual Shark Week.
The 23-time gold medal winner will go up against "one of the fastest and most efficient predators on the planet" as part of a week of programming on the channel which kicks of on 23 July.
Announcing the one-off special Phelps vs. Shark: Great Gold vs. Great White, the Discovery Channel said in a statement: "They are one of the fastest and most efficient predators on the planet: Sharks.
"He is our greatest champion to ever get in the water: Michael Phelps. 39 world records. 23 Olympic golds. But he has one competition left to win.
"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: Great Gold vs. Great White will be shown on July 23. No further details were given by the channel, but those expecting to see Phelps in an Olympic Pool actually racing with a great white may be disappointed, with a composition shot putting the pair against each other the more likely scenario.
Even with his position as arguably the fastest (human) swimmer of all time, with a total of 28 Olympic medals, the chance of Phelps beating a shark in a race is pretty much impossible.
Great whites, who can grow to as long as 5m (16ft), can swim in water at speeds of up to 25mph, whereas multiple world record holder Phelps can has a top speed of 6mph in the water.