Remembering entering San Francisco’s Chinatown in 1962, Robert Stone sees a place unreal. “[I]t was … profoundly Chinatown in no ethnic sense. Rather, the Polanski sense of a lost and terrifying cityscape; its clinky, clunky exoticism, designed to divert the tourists …” Stone calls Chinatown “so rich and strange … I would not spend another such a night though ‘twere to win a world of happy days (Richard III, act I, scene 4). It was like drowning in a vat of the strangest malmsey.” [my bold]
dictionary.com has a definition: a strong, sweet wine with a strong flavor, originally made in Greece but now made mainly in Madeira.
Apparently, Mr Stone is not the first to imagine drowning in a vat of the stuff:
George, Duke of Clarence, being allowed to choose by what death he would die, chose drowning in malmsey wine (1477).
Stone quote source: Prime Green: remembering the sixties by Robert Stone