A ski boat driver who swung a ski biscuit rider into a bridge pylon has been ordered to pay fines, costs and reparation totalling more than $4000.

Tauranga man Daniel Willis, who was 22 when the incident took place on Lake Karapiro in January last year, appeared for sentencing in Tauranga District Court this week on charges of dangerously operating his boat and failing to report the incident to Maritime New Zealand.

The site of the incident where the collision with the pylon took place.

Daniel was taking a group of friends ski biscuiting on Lake Karapiro in his father's boat when the collision happened.

The first incident occurred near the Horahora Domain when one of the biscuit riders being towed narrowly missed striking a protruding branch in an inlet, which was a prohibited zone for power driven vessels.

According to the summary of facts a second incident occurred a short time later as Willis was towing a female rider under the nearby Horahora Bridge, going at well in excess of the five knot speed restriction in that area.

He failed to ensure the biscuit rider was lined up correctly behind the boat as he passed underneath the bridge.

Daniel accelerated when the boat cleared the bridge, which had the effect of propelling the biscuit rider into the path of one of the bridge's concrete pylons.

She tried to avoid hitting the pylon by jumping off the biscuit at the last moment. She then flipped in the water and her left ankle struck the southern end of the pylon.

She tore muscle and a flap of skin on her left ankle. The injury required 14 stitches and ongoing treatment including antibiotics for an infection. She was unable to walk on it or do weight-bearing activity for two weeks and was off work for two weeks.

Daniel's other passengers believe she would have suffered more serious injuries had she been sitting in the biscuit and less able to quickly abandon it, instead of lying on it.

Daniel was convicted by the Waikato Regional Council under the Maritime Transport Act.

Judge Robert Wolff fined Daniel a total of $1000 for these incidents and ordered him to pay reparation to the female rider of $2350.

Judge Wolff fined him a further $500 for failing to report the matter to Maritime New Zealand, commenting how important reporting was when it came to Maritime New Zealand identifying hazards and risks, and preventing further incidents.

The maximum penalty available under the Maritime Transport Act is a $10,000 fine and one year imprisonment.

"The behaviour of this boatie could easily have resulted in a fatality. We encourage people to have fun on the water, but putting people at this kind of risk is unacceptable," says Waikato Regional Council navigation safety manager Nicole Botherway.