"The baby had been in a three-wheel buggy on a slipway beside the family boat.
"He was wrapped in some kind of blanket and I was told he had somehow wriggled around and popped out the bottom of the pram and straight into the water, which is about 3m deep.
"I believe the baby was still in the blanket when he went into the water. Somebody got him out pretty quickly but the poor wee lad must have swallowed some water and no one could do anything."
The local said the infant's parents, Auckland marketing executive Craig Caesar and his wife Gabrielle, were "lovely people" and were at their boat at the marina often in the summer with their other child, 2-year-old Monty.
Marina staff said the family held a boatside service for Carlo on April 30.
A child's teddy bear perched on a small coil of mooring rope and flowers were placed at the back of the family boat.
Long-time Whitianga GP Dr David Wilson arrived at the scene shortly after the infant was pulled from the water and said the baby could not be saved.
Whitianga Marina manager Darryl Smith said the marina board had decided not to comment.
"It was simply a tragic accident and that is the guts of it."
Waikato Police said Victim Support was working with the family but no further details or any public safety messages would be released as the matter had been referred to the coroner, who is investigating.
The Caesar family could not be reached for comment.