Mystery surrounds 'suspicious' deaths of unknown man, woman on Bribie Island

Detectives had many unanswered questions following the grim discovery, which was made about 8.15am on a remote beach, roughly three kilometres away from the northern tip of the island.

Senior Sergeant Scott Wiggins said the bodies were found on the open surf side of the northern tip, but the nearby jet ski was found on the calm side.

Locals have told police it's common for people to park their jet skis or boats on the calm side and walk across to the open side for a swim in the surf.

The bodies were found wearing swimming suits and no lifejackets, with police investigations suggesting they had been in the water for more than 24 hours.

Detectives still had many unanswered questions more than four hours after the first reports of the bodies were received.

Police did not know the identities of the deceased, who owned a jet ski found near the crime scene and whether marks on the bodies were inflicted by the environment or something else.

Senior Sergeant Wiggins said detectives had declared a crime scene after being ferried to the beach by water police, and the deaths were being treated as suspicious.

“There are some marks we are concerned about, but the bodies have been in the water for a period of time," he said.

"It’s possible that the marks on the bodies were caused by the environment."

Senior Sergeant Wiggins said the priority for officers was to identify the bodies and inform next of kin, but no relevant missing person reports had been made.

“It’s a magic part of the world and it is a very sad thing for the community to have something like this happen," he said.

A public appeal for information has been launched in the hope of identifying the deceased.

Detectives have asked for information regarding anyone who was known to be travelling to or from Bribie Island and has failed to return.

Investigations were continuing.