Remove the white rind from the watermelon and cut it into 1- inch cubes; reserve the flesh for another use. Place the cubed melon rind into a large, airtight nonreactive container.
In a large pot over high heat, combine the water, vinegar, mirin, sugar, chiles, lime leaves, star anise, cinnamon, and coriander seeds. Bring to a boil and then immediately remove from the heat. Carefully pour the hot liquid over the watermelon rind, being sure to cover it completely.
Add the ice to the container and allow the liquid to cool to room temperature. Once it has cooled, cover and transfer to the refrigerator for 48 hours to pickle. The pickle will keep, refrigerated, for up to 6 months.