Bring a large saucepan of water to the boil. Add the bitter melon and aubergine to the boiling water and return to the boil; boil for 2 minutes. Drain. Rinse with cold water to stop from cooking further.
Toss the bitter melon, aubergine, carrot, garlic, green chillies and shallot in a large bowl; cover with cling film and set aside.
Stir the water, vinegar, ginger, sugar and salt together in a saucepan; bring to the boil until the sugar has dissolved completely. Set aside to cool completely. Pour the cooled vinegar mixture over the vegetables in the bowl, assuring the vegetables are completely submerged. Cover and refrigerate. Serve cold.