A local who witnessed the crash landing waded out to help the pilot and passengers out of the aircraft.
A boat in the area took the four people to Volcanic Air Safaris' base at the Rotorua Lakefront.
Dorien Vroom from the helicopter company said nobody on board was injured.
"Everybody's out at the moment having coffee."
Ms Vroom did not know how high the chopper was before ending up in the lake or why it needed to make the emergency landing.
Ms Perks said Civil Aviation Authority was securing the scene and investigating what went wrong.
It is understood the helicopter will be winched out of the lake by another aircraft.
Rotorua Fire Service senior station officer Colin Rolfe said it appeared the pilot did a fantastic job landing the helicopter safely.
"It landed upright on its skids," he said.