The man, who was in his thirties, got in to difficulty in the lake this afternoon and police and St John were called to the scene, near Dungarvon St, at 3.02pm.
He was given CPR for some time at the lakefront, but efforts to revive him proved unsuccessful.
In a statement at 5pm, police confirmed the man died at the scene.
"He was given medical treatment at the scene but was then pronounced deceased."
Senior Sergeant Allan Grindell, of Wanaka, said the man passed away after "getting into difficulty in the water".
The cause of death was not yet known, Sgt Grindell said.
A St John spokesman said ambulances were called to the scene, but no-one was transported to hospital.
A police spokeswoman earlier said they arrived at the scene about 3.10pm.
Witnesses described seeing the man being given CPR at the scene after he earlier collapsed in the water.
