We threw a life ring from the side but he couldn't reach it."
Toni's uncle swam after the teenager but couldn't save him.
"I jumped in as well but he was going down and down. We couldn't get to him."
During the service, Mrs Vetemotu said she was trying hard to be strong.
"I have to be strong. I want you all to be strong... I don't have enough words to say thank you."
Additional seats had to be added to the service room for the more than 100 people who came to pay their respects.
Toni's form teacher, Preeti Walia, described him as a "loveable rogue" with a "beautiful smile".
"He made my days very entertaining. He was very strong, very athletic and very popular. His presence will be missed dearly."
Another teacher, Paul Heta, said Toni was a very proud Samoan who was "big in statue and huge in heart".
"He'll be remembered for his cheeky, loving smile and loyalty to his friends and family."
On the rugby field, Toni would often look like he was slacking off, only to reach up, intercept the ball and run down the field with a huge grin, Mr Heta said.
"That was Toni to a tee. Always cheeky; always going about life with a smile."
His classmates also spoke of his positive attitude and thrill for life. After tributes, many joined in a powerful haka. A guitar-led singalong to songs such as "You are my sunshine" ended the service before Toni's body was carried out in a white casket.
Toni is believed to be at least the 18th person to die at the falls, which is listed as dangerous for swimming on Auckland Council's website and also has signs warning of the risk onsite.
Peter Lemalu, 17, died less than a fortnight before the Easter Weekend tragedy and his friend was airlifted to Middlemore Hospital after they got into difficulty in the water.
Mr Lemalu's grieving family have called for urgent action to prevent further deaths at the scenic water attraction.
Safety was reviewed following a 2013 death but experts say better education is the answer rather than trying to implement an outright swimming ban.
