"I kept on shouting for someone to help him. And then he shouted out my name to help him, but I knew there was no way I could."
He then ran over the sand dune and was given a lift on a beachgoer's ute to raise the alarm with the lifeguard patrol on Bethells Beach.
Lifeguards were on the scene within 10 minutes and searchers later combed the coast with rescue boats from Piha and Muriwai and three aircraft, including the Westpac Rescue Helicopter and the police's Eagle.
Zebedee's sister Geraldine, mother Akenese and 1-year-old sister Madison were also at Bethells.
Geraldine, 21, said she sprinted to O'Neill Bay when told her brother was missing, and she could not get the "very vivid" events out of her head. "We even imagine how he must be, right now ... we're just hopeful, and we're praying for him. We know that he's out there somewhere.
"We have a lot of hope at the moment. Some of us are thinking that his body will come to shore. Some of us are praying that he is still alive."
Zebedee's father, Andre, said neither he nor his family had slept since his son went missing.
"We got home about 10pm [on Thursday], we bought some fish and chips. We put it on the table, and none of us have eaten anything yet."
Geraldine said the reality of what had happened began to sink in yesterday morning.
She said her brother, a promising rugby player who was due to start Year 11 at Liston College this year, was "very bubbly and joyful".
"He just loved to smile. That's what my Mum misses the most, what we all miss the most."
She said the family wanted to thank the lifeguards, police, Westpac Rescue Helicopter service, beachgoers, the Bethells community and friends and family for their support.