The Australian endurance athlete John van Wisse set a world-record in 2014 when he completed a gruelling triathlon from London to Paris, running from London's Marble Arch to Dover, swimming the Channel and finishing on a bicycle at the Arc de Triomphe.
His time was an extraordinary 61 hours, beating the previous record by more than 12 hours.
John's record has since been beaten, and John has been attempting to claim back his title.
In both 2016 and 2017, John faced dangerous and debilitating medical injuries while competing, and was forced to withdraw.
Now he's training and ready to try and smash the record again.