A police officer at the scene told the Otago Daily Times the missing man was a father.
Police this morning confirmed that a number of vessels have been searching the water and helicopters have been doing aerial sweeps.
The police dive squad is due to be deployed this morning.
A Glenorchy resident told the ODT yesterday she understood a father and son got into trouble in the water.
A St John spokeswoman said an ambulance, a first response unit and a helicopter were sent to the scene.
One patient with minor injuries was taken to Lakes District Hospital by road.
A second helicopter was stood down before it arrived at the scene, the spokeswoman said.
An ODT reporter at the scene said there were six boats, including some from Dart River Adventures, on the water searching while a helicopter was on a sandbank near the wharf.