Witnesses at the Tahoe Keys Marina say they heard screeching, the sound of tearing metal, and a passenger yell "oh, no!" late Sunday night.
By about 3am Monday, a three-story, $3.2 million yacht so big that it has its own helicopter pad was sunk, one end of it touching the South Lake Tahoe marina bottom at a Titanic-esque tilt.
It's still not clear what sent the Sierra Rose to the lake bed, where it remained partially submerged Tuesday and waiting for a private contractor to remove it sometime within the next few days.
Witness Heather Contreras, who was visiting the marina from Turlock, Calif., told the Tahoe Daily Tribune that more than a dozen people were on the vessel at the time of the screeching noise.
The luxury liner didn't immediately sink, and some people stayed on it for more than an hour after the apparent mishap, she said.
Nobody was injured, marina general manager Robert Spinnato said.
On Monday, a big-screen TV, leather couches and floating slices of bread were visible inside the partially submerged watercraft, which was billed as the largest noncommercial boat on Lake Tahoe as recently as 2006.
Agents listed on the boat's tourist rental website declined to comment to the Associated Press about the situation.
A website detailing the three-room, three-bathroom Sierra Rose for potential renters says it's inspired by the streamlined luxury vessels of the 1930s, but with state-of-the-art amenities.
Features include granite counters, remote-controlled fireplaces, mahogany floors, a spa and custom crystal and china.
The boat rented for $2,000 a night, according to a brochure from 2008-09, or $8,000 for four hours.
El Dorado County Environmental Health Manager Barbara Houghton said the sewage and fuel tanks were sealed and hadn't leaked into the lake, but she said inspectors from the county would be on hand to monitor efforts to pull it out of the marina.
Houghton said that could happen as early as Tuesday.
While the sunken vessel sat unceremoniously in the water, at least a few homeowners in the area were saying good riddance.
Several complained to the Reno Gazette-Journal that they thought the yacht was too big, and blocked views of the alpine lake.
"It's the ugliest thing I've ever seen," Tahoe Keys Property Association front desk clerk Ron Parker said, according to the newspaper. "My idea is it was so ugly someone had to sink it."