"I formed a community group with people in the neighbourhood and last year we had a hui about safety issues at the park," he said.
"Our number one priority was a fence. I put forward my concerns from the neighbourhood to the council and said we wanted some fencing there to prevent more drownings.
"We never got the fence we wanted. They fenced off the culvert but the council didn't have enough money.
"I have been asking myself all night, over and over: 'If that fence had been erected, would this have happened?' I believe it would not have happened."
The boys were with family members at a reserve on Atkinson St.
Mr Jahnke said the toddlers wandered off and appeared to have climbed down the bank to the river.
Sukhraj's mother, Jayme Taewa, noticed they were missing after about 15 minutes and started searching.
Meanwhile a 16-year-old girl found the boys in the water and ran to get help from Achilles' father.
Ms Taewa and Sukhrag's father, Sukhminder Singh, were devastated by his death.
"Mum's broken," said Mr Jahnke. "We're waiting to bring our boy home. He was bright, and bright-eyed. Sukhraj was happy and cheerful. I could tell he was going to be soft-natured, soft-hearted."
Mr Jahnke said he had three siblings and was a "hard case" and funny little boy.
"He was cheeky, and very, very adventurous. He was very loved."
Sukhraj's death brings the drowning toll to 103 for the year up from 72 at the same time last year.
The toddler's family were angry that the area was unfenced.
Mr Jahnke said once the family had farewelled Sukhraj, he would push hard for his safety concerns to be addressed.
Last year, Gisborne District Council staff told Atkinson St residents the council would pay for a fence around the reserve if the residents provided the labour.
General improvements to the reserve were discussed at the meeting, said acting council chief executive Nedine Thatcher-Swann.
She also said money was allocated to the park, and it had been partly used to fence a stormwater culvert on the river edge, and to build a skatepark and a community garden.
"It is inconclusive as to whether fencing the reserve would have made a difference in this case - until we investigate this further," she said.
"Around the country and the world it is very unusual to find our natural environments - rivers, lakes or ponds - fenced."
She said Sukhraj's death was an "absolute tragedy" and extended her condolences to his family.
Sukhraj is the third child to drown in Gisborne in the past 15 months.
Four-year-old Lucas Ward's body was found in the Waimata River in August last year - only 400m from his grandparents' home where he went missing.
In June, four-year-old Whatatutu boy Michael Walker-Mitchell drowned in a ground-level tank filled with more than 10,000 litres of water.
- Additional reporting: APNZ
