The father of a man who drowned in the Waikato River on Sunday says his son could have been saved if the ambulance had not been delayed in reaching the scene.

Benjamin Lucas, 20, from Kinleith, near Tokoroa, was swimming with a friend about half a mile upstream from the Huka Lodge, when he got into difficulty and was unable to get back to shore, police said.

His friend, Daniel Morris, who pulled him from the water, said when the ambulance arrived, it had gone to opposite side of the river, the Dominion Post reported.

When it arrived on the right side, it needed bolt cutters to break through a lock on a fence.

It took the ambulance 20 minutes in total to reach the scene, Mr Morris said.

Mr Lucas' father. John, said the delay might have resulted in his son's death.

But Taupo St John manager Graeme Harvey said the ambulance was only two or three minutes longer than it would have been if it had arrived at the right place at the river.

The bolt cutter was needed because the key ambulance staff had did not fit the lock.

However, the locked gate did not cause a delay because one of the paramedics had a fully equipped mountain bike and rode to Mr Lucas.

He would be asking the council why the lock had been changed, Mr Harvey said.