The Discovery Channel announced earlier in the year that the 32-year-old would feature in this year’s season-opening episode of their annual Shark Week programming schedule.

Axar.az reports citing on Dailystar, Phelps vs. Shark: Great Gold vs. Great White was billed as pitting 23 Olympic gold medals against millions of years of natural evolution.

And last night, the highly-anticipated showdown hit screens in the US as viewers watched Phelps swim 100m with the help of a “monofin” – a shark-like fin attached to his feet.

The "shark" edged Phelps out by just two seconds, but viewers were left seething as it was only a hologram Phelps was racing.