The man was river-surfing the standing waves at the whitewater kayak park above the Camp Hill Rd Bridge about 5.30pm on Monday when he became trapped with his body on one side of a bridge pylon and his board - still tied to his leg by a piece of rope - on the other.
Alpine Kayak Guides owner Ben Yates (40), of Luggate, was waiting to enter the waves on his kayak when he saw a distressed woman on the bank looking in the direction of the trapped man, who was being pushed ''head downstream, feet upstream'' by the force of the flow and was only occasionally breaking the surface to snatch a breath.
Mr Yates - a regular at the park and experienced in rescue situations - paddled to the pylon where he fought to dislodge the surfboard.
''I had to forcefully pull it upstream.''
During the rescue, his paddle and arm became caught in the surfboard's leash and he, too, was briefly trapped underwater where he did some ''fast untangling'' before resurfacing.
Another kayaker, whom Mr Yates recognised as a Queenstown rafting guide, had also tried to release the surfboard but was washed downstream, where he waited and guided the surfer safely to shore once Mr Yates freed him.
Fortunately for the surfer, the water flow had just dropped from about 120cumecs to 75cumecs.
''Had the river been higher, just 10 minutes earlier, he would not have been able to get any breaths and we would have had an unconscious swimmer.''
The man, an English tourist in his mid-20s, was visibly shaken and ''sheepishly'' thanked his rescuers before leaving the scene.
Inexperience in river currents, failure to have a quick-release cord on the surfboard and not wearing a life jacket were contributing factors, Mr Yates said.
''The predicament he was in, it's a case in point of being absolutely ridiculous. He's tied the surfboard to his leg, not on releasable velcro, which is what everyone else uses.
''In a river you wear a life jacket. But surfers ... think of themselves as being on a wave; they don't think of themselves in a river current.
''In the sea you don't have river currents the same unless you're in a rip, and never anything as fierce as what you'd have in a river.''
Although the park was a ''world class feature'' which was teaching local children ''indispensable'' river awareness skills, people needed to appreciate the risks involved.
Visiting tourists often borrowed or bought cheap surfboards to use at the park and it was ''fairly regular that you find people there that this is their first real river experience''.
Mr Yates hoped to install knotted hand access lines on the bridge pylons to allow safe rescuer access and other ''pinning'' victims to self rescue.
Queenstown Lakes district harbourmaster Marty Black praised the efforts of Mr Yates and the other kayaker, who has not been identified.
''[The surfer] was seconds away from drowning ... there was no-one else on the river who could have got to this guy in time and saved him.''
The incident was another reminder of why life jackets were essential for all river users, Mr Black said.
''They save lives. Simple as that.''
