Put the sugar and water in a small saucepan and bring to a boil over medium-high heat, stirring just until the sugar is dissolved; don't stir after that, or the sugar might crystallize. Cook the sugar syrup until it reads 240°F on a candy thermometer (soft-ball stage); this will probably take 20 to 25 minutes. 

Meanwhile, as the sugar gets closer to the soft-ball stage, in the bowl of a stand mixer fitted with the whisk attachment, whip the egg whites until they form soft peaks.

Remove the cooked sugar syrup from the heat and, with the mixer running on medium speed, very slowly drizzle the hot sugar mixture into the whipped egg whites. Continue mixing until the meringue forms stiff, glossy peaks.

Transfer the meringue to a large bowl, add 3 tablespoons of the marmalade, and fold the marmalade into the meringue with just a few strokes, to create orange streaks. Transfer the meringue to a large serving bowl and top with the remaining marmalade, swirling it into the meringue to make a pretty design.

Cover the meringue loosely with plastic wrap and refrigerate for 1 to 2 hours. Serve cold.