A teenager has died after playing a game with friends to see how long they could hold their breath underwater.

Sam Goodenough, 16, of Richmond, died on Tuesday after being on life support in Nelson Hospital for nearly a week. Sam – the only child of Richmond residents Sheryl and Geoff Goodenough – was found floating at the bottom of a residential Richmond swimming pool on December 29.

His funeral will be on Saturday.

Nelson Bays area commander Inspector Brian McGurk said the autopsy showed the cause of death was drowning.

Sam was swimming at his caregiver's pool with other young people.

"Kids he was with thought he was just playing around and he was pulled out and revived by ambulance."

Today, Mrs Goodenough said that her son was a "precious gift from God". She was thankful she got to see him before he died.

"We could pour out our love all over him and kiss him and cuddle him and hold his hand and that really helped because we had that time," she said through tears.

Sam, who had previously been at Waimea and Nayland colleges, attended the Southern Regional Health School at Nelson Hospital and last year received three awards.

"Sam had a smile that could light up rooms. He was like a social butterfly – he had many, many friends. He was just the most lovely boy."

Mrs Goodenough said she was blown away by the wonderful care Sam received while in the Nelson Hospital intensive care unit.

"It was truly amazing."

Instead of flowers, the family is asking that people make a donation to the unit.

His father, Geoff, said it was a tragic drowning and Sam and his friends had been having a competition to see how long they could hold their breath underwater for.

Mr Goodenough said he was getting through with his faith and knew that Sam was in a safe place at a family home when the accident happened.

It has been a deadly holiday period for drownings, with 10 over the official Christmas and New Year holiday period.

The number is tragic yet "sadly predictable", says Water Safety New Zealand general manager Matt Claridge.

The 10 drownings are three more than the five-yearly average of seven between 2005 and 2010.

Mr Claridge said a lot of attention was paid to the road toll but drownings also peaked during this time of year.

"Given the number of incidents where good fortune has contributed to survival, we are lucky that the number of drownings has not in fact surpassed road deaths."

WSNZ is concerned that in most cases lives have been lost because of the failure to follow the most basic of safety precautions.

"Some drownings are tragic accidents but most are due to poor decision making.

"People must take responsibility for their safety and act accordingly.

"Water safety often comes down to using common sense. Lifejackets being worn in boats and constant supervision of young children around water are obvious measures to reduce risk, yet people choose to ignore these facts and consequently they are gambling with their lives."

He said Christmas had been forever tainted with tragedy for 10 families this year and that was 10 too many.

"I urge all people to consider safety as their first priority when enjoying the water. Always ensure the environmental conditions are suitable for the activity planned and comply with all rules and guidelines around safe participation."