Tearful pleas by the family of a teenager killed in a jetski accident failed to stop his his two best mates being convicted yesterday over the death.

The whanau of Rotorua 17-year-old Bishop Thompson, who was fatally injured after falling from a jetski in Lake Okareka in January, never wanted any charges brought against the two boys responsible.

The relatives sobbed in the Rotorua District Court's public gallery yesterday afternoon as lawyers for Ricardo Maaka and Teimana Harrison argued for a discharge without conviction.

Despite emotional submissions from Bishop's family, the boys' parents and their high school principal, Judge Phillip Cooper convicted and discharged them.

The pair, dressed in their Rotorua Boys' High School uniform, held back tears as the judge described what happened in the seconds before Bishop's death.

The three friends were in a group riding three jetskis irresponsibly and at times taking sharp turns to try to splash each other off.

Disaster happened when Maaka, with Bishop on the back, set off across the lake to catch up to another jetski.

"Teimana, you saw this from across the lake and set out to join them. And when the two jetskis were about two or three metres from each other, Ricardo, you performed a tight 180-degree turn which threw up water into Teimana's vision," Judge Cooper said.

Bishop, who was not wearing a lifejacket, was hurled from the back of the jetski and then struck by Harrison's jetski.

The impact inflicted a "massive head trauma". Bishop's body was not found until five days later.

The pair pleaded guilty to charges of driving a craft in a manner likely to cause unnecessary danger to a person or property as soon as they were able.

Through a restorative justice programme, they have met the harbour master and family of Bishop, made a DVD on water safety and given presentations at schools.

Maaka was overcome with emotion as his mother told the court how her son had a "big career ahead of him".

The youths' principal, Chris Grinter, said they had achieved NCEA Level 3 and University Entrance and had shown fine leadership skills.

However, Judge Cooper said the gravity of the offending could not be over-stated.

"Because of the fact that I have to hold you accountable, not just to Bishop's family, but to society as a whole ... and because of the message that needs to be sent about the need for safe boating ... in this case a discharge is not appropriate, in my view."

Later, Bishop's uncle Mana Witoko said he thought the sentencing could have been lighter, "but we have to accept it".

It meant the families could now start mourning "without having to relive that day".

Bishop's mother, Barbie Iraia, said: "We can start the grieving process now ... That's the main thing."