Jaye Lee Walton, 42, faced Ipswich Magistrates Court on Thursday after being charged with domestic violence-related manslaughter over the death of seven-month-old Reef Hunter Walton.
The baby boy drowned on July 12 at a campsite near Gympie, north of Brisbane.
Walton, an Innisfail fishing trawler worker, appeared via videolink in a green jail-issue tracksuit at his bail application.
Magistrate Robert Walker raised claims regarding the baby's drowning, saying witnesses heard the defendant had "thrown him in" to the campsite's nearby lake.
Mr Walker said he did not accept defence solicitor Mark Butler's claim the allegation would ultimately centre on criminal negligence.
"Witnesses were heard to say 'I saw him throw him in'," Mr Walker said.
"It seems to me it's not potentially settled if this would even be the charge."
Mr Butler said the claims, which came second-hand from Walton's partner, were hearsay.
"(Walton's partner) states she said (in response) 'if they saw him, why didn't they come over sooner? Why was I the first person here?'," Mr Butler said.
"She does not believe what she has heard."
Police prosecutor Senior Sergeant Michael Read told Mr Walker investigators were still trying to track down all witnesses.
"Certainly someone has said that to (Walton's partner). It's a matter of how much weight it is given."
Mr Walker told Walton he was facing a strong prosecution case before reading out details of the police's allegations.
Walton had been returning from NSW with Reef and the baby's mother when they stopped at Chatsworth Park on Friday.
"You consumed four litres (of boxed wine) that night," Mr Walker said.
Reef was unsettled the next morning and Walton took him for a walk to the toilet block.
Walton's partner 30 minutes later saw him laying down by the edge of the pond and Reef floating face down about 10 metres out, the court was told.
"She started screaming at you and realised you were asleep. She entered the water and recovered the child. Bystanders came to help," Mr Walker said.
"You woke up and were said to be smiling, laughing and appearing oblivious to what had occurred.
"You then fled on foot but then returned due to the actions of bystanders."
Police said Walton failed to provide a breath sample for alcohol testing.
Sen Sgt Read said he opposed bail due to Walton's alleged actions in custody.
"Remanding him would be for his own protection ... when he was told the child was deceased he said 'there is nothing else left'," Sen Sgt Read said.
Sen Sgt Read said Walton had performed an act of self-harm while in the police interview room.
Mr Butler said Walton had been described as a "loving father" and the alleged incident could be related to alcohol use or lack of sleep.
"(His partner) described his relationship with his son as amazing. He was his first son, he was his little mate," Mr Butler said.
Mr Walker refused bail and ordered the case next be mentioned on August 4 at Gympie Magistrates Court.
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