Lifeless body found on Mexican billionaire's yacht

UPDATE: Greek port authorities are expected to give an update into the death of Australian Instagram influencer Sinead McNamara, whose body was found on board a luxury yacht.

The vessel is owned by Mexican billionaire magnate Alberto Baillères, and has been ordered by the Hellenic Coast Guard to remain docked at the port of Argostoli, on the Ionian island of Kefalonia, while detectives interview crew members and forensic tests are carried out.

An autopsy has been ordered, to determine the cause of Ms McNamara's death.

(Instagram)

Ms McNamara, 20, had been on a dream working holiday aboard the yacht, Mayan Queen IV, for several months in the Mediterranean.

A crew member reportedly found Ms McNamara on board the boat and attempts were made to revive her at the scene, but she died while being flown from the island hospital at Argostoli to a larger hospital in Athens.

Just two weeks ago, Ms McNamara wrote a message on Instagram saying, "My head is all over the shop today. take me back to this where my only worry was not cracking my skull open".

It's not known what lead the 20-year-old to write the post.

View this post on Instagram My head is all over the shop today 🌪🌋 take me back to this where my only worry was not cracking my skull open 💉 A post shared by Salt Bby 💦 (@sineadmcnamara) on Aug 19, 2018 at 6:07am PDT

The owner of the yacht -- 87-year-old magnate Alberto Bailleres -- is one of Mexico's richest men who owns one of the world's biggest silver mines, Fresnillo, among other businesses including retail and bullfighting.

View this post on Instagram Last year in the Mediterranean, can’t wait for this years med season warm weather couldn’t come soon enough 💦 A post shared by Salt Bby 💦 (@sineadmcnamara) on May 10, 2018 at 2:58pm PDT

Local media reported that McNamara was alone with the crew for two days while Baillères left the boat. What happened in the time he was absent from the vessel is now being investigated by Greek authorities.

"The Coast Guard of Kefalonia has ordered an investigation into the circumstances that led to the death of the 20-year-old Australian national as well as an autopsy-necropsy," In Kefalonia reported.

On Saturday, the McNamara family confirmed the passing of their beloved daughter and sister.

"I have unfortunately received the worst news of my life, (Sinead) has passed away," the social media star's brother, Jake McNamara, said according to Daily Mail.

View this post on Instagram 🕊 A post shared by Salt Bby 💦 (@sineadmcnamara) on Jul 12, 2018 at 9:13pm PDT

The Instagram star died three weeks after her 20th birthday, which she celebrated in Greece.

On Tuesday the fun-loving blonde beauty had posted to her 13,000 followers about her jet-skiing adventures on the blue waters of Kefallinia.

Alongside the scenic images are now tributes and comments from hundreds of fans to the influencer, who hails from Port Macquarie in NSW and moved to Sydney five years ago.

"RIP! Sending, love, light, strength & courage to your family," one wrote with a rose emoji.

View this post on Instagram ɲɛbjɛski tiger stripes below 🐅💦 photo from this morning (niebieski is a polish word for beautiful blue, a young polish girl from my last boat taught me it when we were jet skiing around the most beautiful turquoise water in the med last year. It has been my favourite word ever since) A post shared by Salt Bby 💦 (@sineadmcnamara) on Aug 27, 2018 at 8:32am PDT

Another in shock, commented: "I can’t believe it!!"

"Rest In Peace beautiful xx so much love," one person wrote in tribute, while another said: "Fly high gorgeous".

Australian YouTube star Alex Hayes, seemingly in disbelief, announced the loss of his friend to followers via his Instagram Story.

View this post on Instagram 💸 A post shared by Salt Bby 💦 (@sineadmcnamara) on Jul 1, 2018 at 1:16am PDT

Under a photo of the model, Hayes reminded his 650,000 followers: "Life is so precious gone was too soon.

"Such a beautiful human being. Will cherish all our memories. Rest in Peace you beautiful soul."

In a separate post, the YouTuber shared a shot of the pair being goofy, with the message: "Gonna miss ya".