"We loved his curiosity for life, his humour and loyalty, his integrity. His kind, steady and loving presence will be deeply missed."
The "bright-eyed kind" teen leaves behind his 3-year-old younger sister Annie, "whom he adored", and his loving parents Jessica and Greg.
"Family meant absolutely everything to him, he had a very special bond with Annie. She was more than a sister to him, she was his best friend," Jessica said.
A Givealittle page has been set up to help support the family and cover funeral costs.
As of 2pm today, the page had raised more than $7000.
"The Givealittle page was a complete surprise to us, we had no idea until a friend found it and showed it to us a few days ago," she said.
"We were very touched and we are so incredibly grateful for it and will use it to cover funeral expenses."
Sebastian was a pupil at Kaikoura High School, part of a close-knit South Island community who were in mourning over the tragic death.
The school's board of trustees chairman Mark Fissenden last week told the Herald the teenager's death came as a shock not only for his classmates but the wider community.
"It's a tragedy for the school and the whole community," said Fissenden. "And it's a terrible tragedy for the family involved."
He said there were just 200 pupils at the secondary school and everyone had endured more than their fair share of trauma in recent times.
"They've had the earthquakes and Covid and now [lost] one of their peers," he said.
Kaikoura High School principal John Tait said Sebastian's death was incredibly sad.
"This has been a big shock and loss to both Kaikoura High School and Kaikoura Suburban School, as well as our community.
"Our heartfelt condolences go out to the family," he said.
Police attended the incident and the death will be referred to the Coroner.
