St John staff were called to assist an unconscious Mitchell at Hans Bay about 8.30pm but he died despite the efforts of several people, including an off-duty doctor.
An extremely intoxicated 17-year-old girl was taken to hospital.
Officials are waiting for autopsy results to show the exact cause of death as friends and family mourn Mitchell's death.
Professor Doug Sellman, director of the National Addiction Centre at Otago University, said 30 to 40 people died of alcohol poisoning each year, a good portion of which were teenagers "naive to the toxic effects of alcohol".
Schools educate about alcohol, but that wouldn't compete with marketing, Professor Sellman said.
There has been a reduction in alcohol-related harm since 2008 with the slowing economy, he said.
The centre would like the buying age for alcohol to be increase and for more supervision of young adults drinking.
Last night, Mitchell's parents were too upset to talk, but others paid tribute to him. One was Terry Sheridan, on whose farm Mitchell used to work for a contract milker. "He was a good kid. He still came in and saw me on a regular basis."
Mitchell had attended Westland High School in Hokitika before transferring to South Westland Area School at Harihari, 72km to the south.
South Westland principal Ross Brockbank said he last spoke to Mitchell a month ago and the teen was loving his full-time farming job.
"Like all young adults he was exploring his way in the world. He was a young man who had just found his way and where he wanted to go.
"He was enjoying working on a farm and he'd found his place, which is what you always want for your young people, to succeed. He was a good kid."
Family friend Jenny Keogan said Mitchell was always happy and smiling. "He was a twin and he had an exceptionally close relationship with his brother. He also had a great circle of friends. The loss and the circumstances for the loss are absolutely tragic. It's every parent's worst nightmare."
Supplying alcohol to under-18s is an offence.
Greymouth Detective Senior Sergeant Kevin Tiernan said liquor had been bought legitimately from a number of Hokitika outlets.
"Our investigations now are rolling in to who was supplying it and under what circumstances."
Police were yet to consider the possibility of laying charges.
Mitchell's parents had told police their son was not a big drinker. As far as they were aware the most he had drunk in one session before was a bottle of beer, Mr Tiernan said.
"They don't think that he'd ever been drunk."
The police investigation was focused on supply, as the alcohol was sold legally. It would be a couple of weeks before a decision was made over possible police action, he said.
The group had gone to Lake Kaniere to "booze up", although Mr Tiernan had since been told there was one sober person in the group.
He did not know if that was planned or a fluke, but the sober person, a 17-year-old, quickly became overwhelmed.
"He just got inundated with other issues that other people were having.A guy cut his hand taking the top of a beer bottle off, and he's bleeding, and while he was dealing with that a girl was vomiting and while he was dealing with that, Mitchell was turning blue. Clearly, just these people were drinking to way in excess without appropriate help or supervision."
