The Pukete boat ramp is proving popular as a place to launch not just boats, but cars into the Waikato River.

The cars were discovered by police divers just metres from the north Hamilton boat ramp on Tuesday.

"We deployed at Pukete this morning and the first thing we found was seven car bodies at the bottom of the ramp," said Waikato Regional Council spokesman Richard Barnett.

MARK TAYLOR/FAIRFAX NZ A recently dumped car, one of seven, gets dragged from the Waikato River.

By lunchtime, Barnett said two cars had been dragged out.

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MARK TAYLOR/FAIRFAX NZ Members of the NZ Police National Dive Squad secure a towing strop around the axle of a dumped car.

The wrecked and rusted cars, at a depth of up to 6m, were marked with buoys as the dive squad got to work recovering the junk.

"They dive on them, attach towing strops and use their four-wheel-drive truck to tow them out," Barnett said.

"Then we get a scrappy [scrap metal dealer] to come along to take the wrecks away."

MARK TAYLOR/FAIRFAX NZ The Police National Dive Squad drag a dumped car from the Waikato River at the Pukete Boat Ramp in Hamilton.

Barnett had no idea so much junk was in the river.

"It was a surprise," he said.

"It's going very well. We're pleased because we don't know what's there."

One of the cars still had its number plate attached. The second car fished from the murk was "a pretty old" Mini, which came out in two pieces.

He couldn't speculate on how the cars ended up in the river, but said it's possible some had been stolen or dumped by their owners.

Vehicles that crashed into the river in a road incident are recovered at the time of the police investigation, he said.

Waikato's harbourmasters patrol from Port Waikato to the bottom of the Huka Falls near Taupo and there are numerous places where large items can be dumped.

"Around the bridges would be an important place to look to," Barnett said, "anywhere where there is vehicle access."

Wrecks are an environmental concern and pose an underwater hazard for boaties and river users, but Barnett said there are limited ways to locate them.

"We've got good sonar on one of the boats, but it doesn't pick up the detail well enough," he said.

"There is so much natural debris - river bed, trees and so on."

The Police National Dive Squad was asked to join the exercise run by the Waikato Regional Council, Waikato River Authority and Hamilton City Council and help out for three of its members' annual training days.

They would have to leave if duty called, Barnett said.

"We saw a way where the council and river authority could provide some financial assistance in our area so they could use their expertise to help pull some of the rubbish out of the river."