The mother of a man killed in a boating incident in Tauranga harbour is calling for stricter laws to be made regarding intoxication while driving a boat.

Lisa Graves' son, Clayton Graves, was killed on October 4, 2019, after his friend Guy Appleton took him for a boat ride after midnight.

Appleton crashed into rocks, causing Clayton to be ‘flung into the windscreen' resulting in ‘substantial internal bleeding' from tears to the liver and kidney, according to Justice Gordon's pre-sentencing remarks.

He was then 'left to bleed out” while Appleton failed to get help, according to Lisa's victim impact statement.

She describes her pain as 'immeasurable”.

'If you're the captain of a boat don't drink.

'The loss of my only son will forever affect me in ways I can't imagine, from a senseless and preventable act.”

Under Maritime NZ rules, you can be prosecuted for operating a boat in a manner that causes unnecessary danger under section 65 of the Maritime Transport Act.

'As a skipper, you're responsible for the safety and wellbeing of everyone on board your boat. A responsible skipper will never operate under the influence of alcohol or allow an intoxicated person to operate their boat,” says a statement on the Maritime NZ website.

'Skippers on board a vessel should always be capable of performing any tasks required of them. This is particularly important on the water, where an emergency requiring action may arise at any time.”

In Tauranga High Court on Wednesday, Appleton was sentenced to a minimum of two years and seven months in prison after earlier pleading guilty to manslaughter.

During sentencing, Justice Christine Gordon says the principal aggravating factor was his consumption of alcohol.

'Mr Graves died in circumstances that were entirely preventable. Your actions went beyond careless, they were reckless.”

She says Appleton's speed was four times over the legal limit, resulting in the crash.

He did not use GPS, a first aid kit, nor attempt to call for help, says Justice Gordon.

Instead, Appleton sat on the rocks for around six hours, before passerby's approached.

'Passerby's came, but you said ‘no he's fine, he's asleep'.”

At around 7.20am another member of the public came by who noticed Clayton was 'in a bad way”.

When emergency services arrived, they estimated he had been dead for about 4- 6 hours.

In her pre-sentencing remarks, Justice Gordon said Lisa's pain was 'insurmountable”.

'Every day she feels her son's death. The ongoing suffering is emotional, psychological, and physical.”

Justice Gordon says Appleton 'failed to fully grasp the enormity of the repercussions of his actions”, and there was 'limited genuine regret identified”.

Lisa says she tried to reach out to Appleton expecting an apology, but 'got nothing”.

Appleton's defense lawyer expressed deep condolences on behalf of Appleton, saying his remorse was genuine but he had trouble expressing his feelings.

He says he was 'dazed and confused” and did not appreciate the seriousness of the accident.

'If he has no recollection there's little else he can say, and while that's unacceptable from the family's point of view, it is what it is.

'There's no textbook to how a person should react in such a situation- this should not be mis-interpreted as a lack of remorse.”

Justice Gordon says manslaughter consists of killing someone by an unlawful act, which in this case was exceeding 5 knots within 200m of a shoreline or structure.

Appleton was estimated to have a blood alcohol level of between 110-220mgs per litre.

He has two previous convictions for driving carelessly.