Police say they are "holding out hope" that a large-scale air and sea search will uncover the whereabouts of missing Brisbane fisherman Trent Riley in Moreton Bay.
Mr Riley's empty boat was discovered motoring 100 metres off Mud Island near the Port of Brisbane on Wednesday afternoon.
The 26-year-old's disappearance has sparked a major search operation, involving Water Police, the Coast Guard, Volunteer Marine Rescue and Mr Riley's friends.
Acting Inspector Mark Mooney said police had been in contact with the missing man's mother.
"She's aware the survivability after 24 hours is quite low which is very heartbreaking for her and the family and friends," he said.
"We're still holding out hope that we'll bring him home alive to her."
Mr Riley posted a video to social media two hours before his empty boat was found.
"I understand he is quite a keen fisherman, however he doesn't normally fish in this area," Acting Inspector Mooney said.
"The vessel itself is quite small and I wouldn't say it would be an overly safe vessel to go out in Moreton Bay."
Fifteen boats and two helicopters have been involved in the search.
Acting Inspector Mooney said the man had not been wearing a life jacket and it was unclear how he had fallen from the boat.
The aluminium vessel was not damaged, but Mr Riley's mobile phone and a fishing rod are missing.
Police have urged anyone who saw the fisherman's boat between 1:30pm and 3:30pm on Wednesday to contact authorities.
