Asked what her son was doing on the night of October 10, she said the boys had gone to Omokoroa with the impression they could borrow a boat from one of the boy's brothers.
"But when they got out there he said it was too rough and they couldn't take it out so they just borrowed one that was there."
"They were always going to put it back."
The boys Shaun was with on that night were old friends, although Shaun rarely hung out with them, she said.
His mother said Shaun, nicknamed Shauni, had "grown up" and perhaps his friends hadn't.
"He didn't look at their faults, he looked past that and took them for who they were. He was that kind of a guy.
"He had a genuine warmth about him ... and he would never say a bad word about anyone else."
One of the men on board, Kane, had known Shaun and his family since they met at primary school.
"Liam has been a part of the family for so long, since they first got together he's been a part of the family. He was one of Shaun's special friends. They go way back," Mrs Shearer said.
She didn't want to talk about how she felt that Kane had purposely disappeared after the accident, but said he must be going through "something major".
"They were best friends for so long so he must be going through something major too."
After the incident, Mrs Shearer said the family had lived in hope that Shaun would be found alive. She thanked the efforts of Tauranga police and everyone involved in the search.
Shaun was born on February 16, 1989, in Tauranga - the city he's lived all his life.
Between his mum and step-father, Kevin Shearer, Shaun was one of eight children in the large, combined family.
He had a strong relationship with his younger brother Eone (Ethan). His sister Natasha said even though Shaun was younger than her, he always looked out for her like an older brother.
For his 21st Shaun asked to have a barbecue with 12 people and about 112 turned up, Mrs Shearer said.
"He was just a well-liked kid.
"He was the best son and brother. He had huge potential and he was truly loved."
Shaun went to Otumoetai Primary, Intermediate and College before he got a job at the Port of Tauranga as a stevedore - a role he's had for the past three years. He worked the 3pm to 3am shift.
His step-dad said: "I had to take him and pick him up every day ... and he was so polite. Every time I dropped him off he said 'thank you'."
His long-time girlfriend, Ashlee, said Shaun loved his job and loved life.
"We've been together four years. We met at a friend's place and he had his eye on someone else, but I snapped him up. It was his personality [that attracted me to him], he was always cheerful and very entertaining," she said.
The 21-year-old said they had recently returned from a holiday in Australia, which cemented their four-year relationship.
"We didn't live together but we had plans on it. He was a saver and he had applied for a home loan for us. He never wanted to go renting, he thought it was a waste of money and being together gave us an opportunity to start saving for a house. That was my plan, but then it became his plan too."
"We had started to go out, looking at places [and] we were really excited about it."
She said Shaun had "a genuine warmth" about him and he would never be forgotten.