However, it was not a straightforward contest on Saturday, as Simon O'Donoghue (51) was swimming while Aiden McAvinue (40) was running his first ultra-marathon, taking part in the fifth Round-the-Rock Ultra Marathon, both to raise funds for the Grace Crocker Family Support Foundation.
In the end they finished within a hour of each other, with Mr McAvinue, the foundation's chairman, taking first place.
Starting from the Steam Clock, he completed the 48-mile course at West Park in a time of 9 hours and 54 minutes – to greet Mr O'Donoghue, who swam 45 miles from Elizabeth Castle in 10 hours 41 minutes.
The prize for the winner was a welcome pint of ice-cold beer.
Mr McAvinue was running solo while Mr O'Donoghue was accompanied by Craig Swart and Toni Boucholtz.
The two friends were level when they reached St Ouen's Bay, then Mr McAvinue pulled away.
He said: 'I was less bothered about beating Simon – the swim was the bigger challenge.
'I was just delighted to come in under ten hours, as that is a silver medal in ultra-marathon running, and I had never run more than a half-marathon before.'
In addition to the friends' personal battle, four paddleboarders, 11 relay teams of five runners each and two more swimmers, including St Brelade Constable Steve Pallett, were also raising money for the Grace Crocker Family Support Foundation.
During the event, Mr Pallett became the oldest man to swim around Jersey.
Although he lost the challenge, Mr O'Donoghue still had cause to celebrate, as he became the 99th person to swim around Jersey.
He said: 'We are going to do it all over again next year, and we want to make it an annual event.'