Yesterday Mr Marriott said he wouldn't be surprised if people reacted negatively to his taking Elijah skydiving, but the boys had been around the sport for most of their lives and were therefore different from other children.
"They've seen hundreds of jumps and to them, it's normal," he said.
"I don't think I would take any other person's child ... It's just something special I can do with my boys."
But experts said the dive was dangerous because of the boy's age and lack of life experience.
Skydiving expert Wendy Smith, who has been involved in tandem skydiving for more than 20 years, said she was a good friend of Mr Marriott, but was very much against the idea of his jumping with his 2-year-old son.
"We have to be very careful in the sport with letting very young children [go]," she said.
"They still have a problem with structuring and growing of their brains. The freefall and the opening can cause quite a radical shift of the cerebral fluids," Ms Smith said.
The youngest child she had taken tandem skydiving was aged 4. Others included 7-year-olds and 10- and 11-year-olds.
"It is not healthy for a child younger than perhaps 4 or 5 to do a tandem because the harness doesn't fit their small body ... It can imbalance them and actually cause them damage [in the brain]."
Developmental paediatrician Dr Rosemary Marks, who is the president of the Paediatric Society and a doctor at the Starship children's hospital in Auckland, said it was certainly something she would not recommend to parents.
She said that at 2, Elijah was still developing and, more importantly, was too young to understand exactly what he was getting himself into.
"As an adult, we know what is appropriate for children and what is not appropriate," Dr Marks said.
"Just because a child asks for something ... adults should have the wisdom to know what's appropriate."
