Line a baking tray with non-stick baking paper. Cut half the watermelon into 2cm pieces. place, in a single layer, on the prepared tray. Place in the freezer for 1 hour or until frozen.
Coarsely chop the remaining watermelon. Blend in a blender until smooth. Strain the watermelon puree through a fine sieve into a jug, gently pressing with the back of a spoon. Discard any solids. Place the watermelon juice in the fridge to chill.
Stir the sugar and lemon juice in a punch bowl or large serving jug until the sugar dissolves. Stir in the watermelon juice, ginger ale, vodka and wine until well combined. Stir in the mint and frozen watermelon pieces.