An hour of open water is the best opening act anyone ever booked. You leave the mainland, the harbor drops behind you, and by the time the island comes up out of the haze you have stopped being a person with a commute. The ballroom is waiting at the other end. Art deco, round, about a thousand reserved seats, close enough to the players that the intimacy is real rather than claimed, with acoustics that make it one of the most beautiful rooms in California. Contemporary jazz has filled it every October since 1987, smooth jazz and R&B jazz and fusion across a full weekend twenty-six miles offshore. This one …