Experienced lifeguard and search and rescue squad member Ryan Craig (42) left the trial to rescue the struggling surfer, who could not reach shore because of strong currents.
Mr Craig helped rescue the 40-year-old in an inflatable dinghy, before returning for the trial.
Facing competition from about 60 others for 18 paid lifeguard spots during the summer holidays, from many less than half his age, Mr Craig said he took nothing for granted, despite his experience.
St Kilda teen Nic Brice (16) hoped it would be third time lucky for him, after trialling unsuccessfully the past two years.
The competition was pretty tough, he said.
The hopefuls competed at the St Kilda Surf Life Saving Club, taking part in a 400m swim, 3km run, CPR demonstration, theory test, a run-swim-run, and a tube rescue.
Surf Life Saving southern region programmes and services manager Dougal Holmes said as well as the 18 paid spots for Dunedin beaches, this was the first year a new system was in place to trial guards for all surf districts.
The change meant university students from the North Island or upper South Island could trial in Dunedin for where they intended to spend summer.
Otago and Southland club development officer Stephanie Laughton said a high point of the 2010-11 season would be St Clair's centenary of its voluntary life-saving patrol, in April.
Kaka Point, Warrington, Brighton, St Kilda and St Clair beaches are patrolled.
The guards start on December 20, Monday to Friday, 11am to 7pm, until January 28.
Volunteer guards would also be on patrol from October 30 to March 13, Saturday and Sunday, 12pm to 5pm.
