RIO DE JANEIRO — The debate over the greatest modern Olympian and fastest human will be decided later this month when Michael Phelps and Usain Bolt race in a 100m exhibition in a swamp.

Representatives for both athletes reportedly spoke on Monday, the day after Bolt won his latest 100m gold medal. Phelps swam his last race on Saturday night. Details were quickly hashed out and both parties agreed to a race later this month in a swamp in the Florida Keys — approximately halfway between Phelps’ home in Baltimore and Bolt’s home in Jamaica.

“They each respect each other very much, but they’re also ultra-competitive,” said a USOC representative who was privy to the discussion. “Each wants to prove he’s the best.”

The race will stretch 100 meters in swamp land that is an exact 50/50 mixture of soil and water. Bolt won’t be able to run through at high speed without navigating some water, and Phelps won’t be able to swim the course without some upright trudging on his legs. The race will be broadcast on pay-per-view with a donation made to charities that benefit children who are slow.

“We’ll know once and for all who the greatest Olympian is,” said Phelps. “I’m excited to make my case. And I’m excited to compete against another human. In the old days, retired Olympians had to race dolphins to make money.”

Olympic gymnast Simone Biles is also reportedly interested in competing. She would be required to make her way through the swamp via jumps and flips and landing on any small pieces of sticks protruding up out of the mud.