About 20 volunteers are expected to help with today's search effort, Tonkin said.
"We've got to keep going because Magenta's been a tower of strength - his sister - and Reuben, the brother, he's beside himself... The father's devastated."
The 14-year-old mate Jack had been swimming with when he went missing was distraught, but was being supported by whanau, Tonkin told the Herald.
"He's devastated because he said 'I caused it'. We're like 'no you didn't, it's just an unfortunate sequence of events'. But we're dealing with a 14-year-old juvenile which this is his first big wake-up call to the reality of the world."
Tonkin said he and others close to Jack had accepted that the Linwood College student had probably drowned, but Sue Sutton was hopefully her son would be found alive.
"The mother's just maintaining that we expect him to walk in through the door thing - but realistically we know that's not the case. It's just to bring the body home and bring closure to the whole tragedy."
Police said on Tuesday night that it was now a body recovery operation.
Tonkin said he hoped to borrow a camera drone today so he could conduct an aerial search.
"If [a drone] could go up high enough at oblique angles in the water we'll probably find him because it's a lot calmer today. And hopefully we can get someone in a jetski out on the surf line zooming around."
The search effort would concentrate on the Brighton side of the beach today.
The response from the Sumner community had been "phenomenal" during the past six days, Tonkin said, and family and friends were appealing to members of the public in the area to continue to keep an eye out.
"It's just a case of if you see something, for god's sake *555 or 111," Tonkin said.
"You never know what's going to happen today but hopefully we get closure this weekend. Sue, I don't know how she's doing it. She's running on empty. But a mother's love is a mother's love I suppose. All we want is for us to find closure in this and bring him home.
"To know that young man and all the challenges ahead of him and all the life that he's not going to have - it's damn devastating when a 14-year-old boy is just gone."
A Givealittle page has been set up to fund a light plane to help with the search effort.
To donate go to: https://givealittle.co.nz/cause/jack-sutton-search