A German tourist who had to be plucked out of the Clutha River on Sunday also managed to escape out the back of an ambulance on the way to hospital.

Alexandra Police Acting Sergeant Graham Perkins said the 32-year-old man was picked up by two local jet skiers 2km south of the Alexandra bridge in a hyperthermic condition.

After dropping his backpack off at Community House, the man went walking on the Millennium Track and decided to take his clothes off before entering the river.

The two men that found him in a strong current said most of his head was submerged and he was very white. 

They managed to pull him up onto the back of the jet ski.

Acting Sgt Perkins said ambulance and police were waiting near the boat ramp, and he was shaking severely and was initially incoherent because of the time spent in the cold water.

“His body temperature had dropped drastically,” he said.

One of the Otago Southland Rescue helicopters also arrived onsite, but a paramedic assessed him as suitable for transfer to Dunstan Hospital in an ambulance instead.

Enroute to Dunstan Hospital the man managed to undo his seatbelt and when the ambulance pulled over and officers attempted to restrain him, he opened up the back door and took off naked towards the river again - near the Alexandra Golf Course.

Realising he couldn’t get through because of the 4WD tracks and willows blocking the river access, he turned back and was arrested by police who had arrived on the scene.

Acting Sgt Perkins said the man was transferred to Dunedin for a psychiatrist assessment.

Family in Germany were also contacted.

“He was very lucky to be found. I have big praise for the local jet skiers for their attention and observation,” Acting Sgt Perkins said.

The second rescue helicopter that landed in Pioneer Park on Sunday was transferring a young motorbike rider to an ambulance so he could be taken to Dunstan Hospital, following an accident.