EXCLUSIVE NEWS FLASHBACK: A nasty fight nearly sank Lisa Marie Presley’s marriage to Nicolas Cage after Ersatz Elvis got bombed and belligerent aboard his yacht off Catalina Island weeks before the wedding — and Fiery Fiancee furiously flung her $65,000 diamond engagement ring into the briny deep . . . where it still sparkles with the fishes! The high seas horror unfolded one dark night during a vacation aboard Cage’s yacht, “The Weston.” Skipper Nic got heavy into the rum, then started snarling and ranting at his bride-to-be when she complained about his boozing! Shaking with rage, Lisa Marie screamed she was breaking the engagement, took off her ring — and hurled it into the sea! Horrified Cage howled, “That was a $65,000 f—ing DIAMOND!!” He freaked, phoned pro divers even though it was the wee hours, and offered big buck$$ to recover the ring. Lisa Marie helicoptered back to LA, but Cage — in a panic, say locals — stayed to supervise the search. After two days scouring the ocean floor, divers told Cage it was hopeless — and the star faced the stone-cold sober truth: Write off the rock and resuscitate their drowning romance! The couple kissed, made up and intend to Live Happily Ever After!