Mrs Ealam told the court there was no hope of rescuing Tayne, as he was completely submerged. The listed cause of death was drowning.
Mr Bowes told police he had two beers prior to the accident, while installing a play hut for his daughter.
His wife Katrina was unaware of any health problems at the time, but Mr Bowes had mentioned "pins and needles'' in his hands for several days prior. He was later diagnosed with a brain tumour in his right temporal lobe.
Medical professionals said this could have affected his ability to judge space and distance.
A breath test some hours after the accident revealed Mr Bowes had a breath-alcohol level of 250 micrograms per litre of breath, which would have put him at 360 to 479mg at the time of the accident. The legal adult limit is 400mg.
Police decided that alcohol was not a major cause in the crash.
Mr Bowes was in an extreme emotional state after the accident and had difficulty remembering what happened.
He told police he had been going slow down the track and thought he had his foot on the brake when the truck began to slide down the steep slope into the pond. He said he thought he had done everything he could to stop it.
After the car was submerged, he nearly gave up but managed to free himself.
He said he did not know how to get to his children and feared he had hurt Tayne as he struggled to escape.
Mrs Ealam said there were no suspicious circumstances surrounding the accident.
She fought back tears as she spoke of finding Keira alive and pulling her from the car.
The coroner commended her and Mr Glue for their excellent work in searching for the children.
"It is clear they performed to the highest standards,'' Mr McElrea said.
The children's grandfather, Murray Bowes, said the accident scene was treated as a recovery rather than a rescue, and it was more than two hours before Keira was rescued.
Mrs Ealam said they had to consider their own safety and "we acted as quickly as we possibly could''.
Mr Glue said that in hindsight, he agreed with Mr Bowes that he should have got into the water sooner: "But the result would unfortunately have been the same for Tayne.''
Mr McElrea said police had responded properly at the scene and Mr Glue was being too hard on himself.
The inquest is proceeding.