A family of Australian tourists had an unfortunate dip in Masterton's Henley Lake last night when their campervan ended up in the drink.

The family, parents with four children aged between 3 and 16, had arrived in the town last night.

Senior Sergeant Mike Sutton said the mother had got out to stretch her legs, and the father was probably planning to do the same.

"Except they still had [the vehicle] in gear and didn't have the brake on and it went forward into the lake with five people inside."

Members of the public looked after the mother until police, fire, and ambulance arrived.

Sutton said the family remained remarkably calm.

A firefighter waded out about 20 metres to the campervan, attaching a rope.

Then a nearby waka ama was used to float the father and children to safety on the shore.

They were checked over by ambulance staff at the scene. No one was taken to hospital.

"The kids were in really good spirits," Sutton said.