Model's worrying Instagram post before mystery death on billionaire's yacht

The Sydney model who was found dead on a billionaire’s superyacht in Greece had shared a cryptic Instagram post with her followers just two weeks before her death.

Sinead McNamara, who turned 20 last month, allegedly died aboard the Mayan Queen IV where she was working as a crew member.

Exactly two weeks before her death, the model posted a photo taken back in June of herself smiling while riding a quad bike along a Greek cliffside.

Accompanying the image she wrote: “My head is all over the shop today. Take me back to this where my only worry was not cracking my skull open.”

The Instagram model’s death was confirmed by her friends on Sunday, as tributes flowed into her social media pages.

A post on Ms McNamara’s Facebook page tragically revealed her sister was due to touch down in Greece the day after she died.

Her cause of death has not been confirmed.

Ms McNamara, originally from Port Macquarie in NSW, was found in a critical condition before being transferred to a local hospital, the Sydney Morning Herald reports.

She later died on the way to a hospital in Athens.

The six-storey ship, valued at about $195 million, belongs to Mexican mining magnate Alberto Bailleres and must now stay in port until an investigation – including an autopsy – wraps up, Greek media said.

Mr Bailleres had left the yacht, leaving Ms McNamara on board with the rest of the crew, local media reports.

Two days later, her body was found.

The Department of Foreign Affairs and Trade confirmed on Sunday it was “providing consular assistance to the family of an Australian who died in Greece”.

Ms McNamara’s friends posted tributes to her throughout the weekend.

“I lost a girl who opened my mind to the world,” one friend from Port Macquarie wrote on Facebook on Sunday.

“Can’t believe I was talking to you less than a week ago organising to meet in Greece … Rest you adventurous crazy girl!”