Sunk Yacht Update

From the Tahoe Daily Tribune: A three-level, $3.25 million luxury yacht sank at a dock in the Tahoe Keys Marina early this week.
On Monday morning, the Sierra Rose sat partially submerged at its prominent location near the mouth of the marina.The floating dock leading to the vessel jutted out of the water at a 45-degree angle. The lowest level of the 86-foot yacht was completely underwater, while the second level of the vessel was partially submerged. The yacht remained in a similar position Tuesday afternoon.
And what a yacht it is:  The Sierra Rose sold at auction for $3.25 million in August 2008. The handcrafted mahogany luxury yacht boasts three bedrooms, three and a half bathrooms, granite fireplaces marble tile floors, an outdoor Jacuzzi Tub and a helicopter pad. As recently as 2006, the Sierra Rose was billed as the largest noncommercial boat on Lake Tahoe.
The vessel can hold about 100 guests comfortably in the summer months, according to a online 2008-09 rate sheet. Renting the vessel for a four-hour private event cost $8,000 at the time. Taking the Sierra Rose on the lake requires a licensed captain, according to the rate sheet.
The vessel was brought to Tahoe in three pieces and assembled on a barge at the Tahoe Keys Marina in the winter of 2005, according to a August 2006 article in the Tribune.
http://www.tahoedailytribune.com/article/20120709/NEWS/120709922/1068&ParentProfile=1056
According to witnesses, they heard a loud metal scraping/tearing sound, but those on the boat didn't hear anything, which seems kind of strange.  But they haven't raised the yacht, so they won't know what happened.