Pour water into a large saucepan, add sugar. Cut the vanilla pod in half lengthwise, scrape the vanilla seeds with the tip of a knife into the water with sugar, put the pod itself in the same place. Bring to a boil over low heat, cook for 7-10 minutes.
Meanwhile, peel the ginger and cut into thin slices. Remove the zest from the lime in thin strips, cut the lime itself in half, squeeze out the juice.
Put the ginger slices into the prepared syrup, add the zest and lime juice. Remove from heat, cover and cool completely, 1 hour.
Cut the rind off the melon and remove the core. Cut the pulp into small cubes.
Put the melon cubes in the ginger syrup, mix. Cover and refrigerate for at least 2 hours.