The rider was nowhere to be seen.
"I was a bit annoyed because I already told the guy this would happen," Mr Ritani, 16, said.
He then radioed for help and lifesavers Mac Hepburn and Caitlyn Duffy responded in the club's IRB.
Mr Hepburn, 19, found the man with his hand in the air 150 metres away from his jetski.
Fortunately the man was wearing a life jacket and the pair were able to haul him in and tow the jetski back to shore.
Despite the high winds, Mr Hepburn said they were confident of rescuing the man safely.
"Before you go out, you need to be sure of self-preservation - and we were," he said.
The man did not appear overly thankful but did say he was "exhausted" after the rescue, Mr Ritani said.
Mr Hepburn and Miss Duffy are regional lifeguards and train every morning in summer for IRB rescues.
"We train for those particular situations all the time, though this is the first rescue for the season for me," Miss Duffy, 22, said.
All three lifeguards are experienced, with Mr Hepburn coming up through the nippers system and gaining his lifeguard certificate at age 14.
This is his first year as a regional lifeguard and he is relishing the opportunity to pass on some of his knowledge to the nippers.
"It's good to see the kids coming up the ranks," Mr Hepburn.
All three lifeguards will be on duty at Riversdale Beach this summer and hope that beach-goers will heed their advice when warnings are issued.
