He then saw a broken post, which was enough for the men to turn their car around.
"It takes quite a lot of force to break one of those posts [and] something in my head just clicked."
He climbed down the bank and came across a trail of items, including a camera bag, cellphone and a pair of sunglasses, which led him to a car, with the Wanaka man still trapped.
Fearing he would find a body, he saw the man move, then alerted emergency services.
"I held his head still so he could keep breathing and just sat there and waited, it seemed like forever ... it's not something I've done before."
Mr Smiler said when he found the man he was breathing quite well, but "when the ambulance came his breathing was really shallow".
"It was quite emotional. It's not something you want to come across."
Police last night praised Mr Smiler for his alertness.
Wanaka and Queenstown police attended the scene, along with two St John ambulances and two Queenstown fire trucks.
After the man was extricated from his car, he was airlifted from the scene at 1pm by a Southern Lakes rescue helicopter, first to Lakes District Hospital then to Dunedin Hospital.
Police contacted his family in New Zealand and Japan.
Sergeant Derek Ealson, of Queenstown, said the cause of the crash would be investigated.
St John Southern Region communications co-ordinator Alena Lynch said the man had multiple life-threatening injuries and it was fortuitous he was found as the vehicle could not be seen from the road.
A Queenstown police spokeswoman said the weather was fine but chilly, with temperatures dropping to about 4degC overnight.
