The 421 is a pressurized piston twin with a service ceiling of around 30,000 feet and a regulatory ceiling of 28,000 feet. They are typically flown in the low flight levels.
According to the AP, the airplane went down around noon approximately 120 miles West of Tampa, “landed softly” and remained upright and intact. A Coast Guard rescue helicopter was deployed to the crash site, but was not expected to arrive while the airplane was still afloat. There were reportedly no signs from the site that the pilot was still alive.
The airplane had flight planned for 27,000 feet and 215 knots along a Gulf of Mexico high-altitude route. The flight from Slidell, LA, to Bradenton, Florida, was expected to last around three and a half hours.
While the exact cause of the incident is still unknown, references to the 1999 crash that killed golfer Payne Stewart and five other occupants aboard a Learjet after the aircraft lost cabin pressure over the Gulf of Mexico have already begun."
http://www.flyingmag.com/technique/accidents/unresponsive-cessna-421-pilot-crashes-gulf-mexico 