Pop icon OLIVIA NEWTON-JOHN is reeling over the revelation that her debt-ridden “dead” boyfriend faked his fatal drowning in 2005 – as discovered in secret government documents obtained by The National ENQUIRER!

Patrick McDermott was 48 years old when he boarded a charter fishing boat for an overnight trip off the California coast. He had disappeared when the ship returned to dock on July 1, 2005.

Now a secret Coast Guard report is in the hands of The ENQUIRER, and threatens to capsize the new life built by the grieving “Grease” star – who married businessman John Easterling in 2008.

“Olivia is living a nightmare,” a close family friend revealed to The ENQUIRER.

“She had finally healed from the trauma of Patrick’s disappearance and made a new life with John.

“Now she’s learned Patrick’s still alive, and her whole world has come crashing down.”

The distraught pop star originally used all of her celebrity clout to plead for information about her missing lover.

The media explosion spurred an extensive search by the U.S. Coast Guard Investigative Service [CGIS] – officially closing with a November 2008 report that Patrick “most likely” drowned.

New bombshell government papers, however, reveal that the CGIS kept the files open on the missing man, after a routine check revealed that the State Department had Patrick on the “Dead Beat Parent Lookout” list to “prevent him from obtaining a future passport.”

Investigators began to speculate that Patrick, who was $35,000 in debt and owed child support, had disappeared for financial reasons.

Meanwhile, a heartbroken Olivia was inconsolable – later confessing that she had popped antidepressants for three months, “until I could see the light again.”

The Coast Guard documents expose even more about the depths of Olivia’s depression. The pop star had been having romantic problems with Patrick, and was hoping to rekindle their on-and-off relationship of nearly nine years.

The hidden CGIS papers – obtained by The ENQUIRER through a Freedom of Information Act request – are heavily censored, but reveal that Patrick has been spotted at least a dozen times in locations ranging from Alberta, Canada, and Cabo San Lucas, Mexico, to the tip of Baja California.

FOR the FULL STORY with ALL the details – it’s only in the new ENQUIRER – on sale now!