Update (1242ET):

The Wall Street Journal cited Italian Coast Guard officials who said British tech entrepreneur Mike Lynch, Morgan Stanley International Chairman Jonathan Bloomer, and Clifford Chance lawyer Chris Morvillo are presumed dead after a superyacht they were chartering was hit by a waterspout before capsizing off the coast of Sicily early Monday. 

Here's more from WSJ:

One of Lynch's daughters, Bloomer's wife, Judy, and Morvillo's wife, Neda, also were among the missing.

Authorities confirmed the body of the yacht's cook had been recovered.

The coast guard said the bodies of the missing are likely trapped in the yacht. Rescuers were reassessing how to access the wreckage, after the first inspection by cave divers was blocked by debris, the coast guard said.

"The space is very tight, because everything fell when she capsized," Luca Cari, the head of Italy's national firefighters' corps told reporters. "Divers are trying to remove furnishings, wires and other debris to clear the passageways."