1. Using a vegetable peeler, cut the zest from one of the oranges in wide strips and then into matchstick strips. Put the zest in a medium saucepan with the water and sugar. Simmer until the zest is translucent and tender and the liquid is reduced to approximately 2/3 cup, about 25 minutes. Strain out the zest, reserving both the syrup and the zest. Squeeze 3/4 cup juice from the oranges, strain into the syrup, and chill in the refrigerator.
2. Core each half of the pineapple by making a diagonal cut on one side of the core with a long serrated knife. Make a diagonal cut on the other side of the core, forming a V. Remove the core. Turn the halves over and cut the pineapple crosswise into 1/8-inch slices. Arrange the slices on four plates in concentric circles.
3. Pour the orange syrup over the pineapple slices. Put a scoop of sorbet on top of the pineapple and the candied zest over the sorbet. Garnish with the mint.