Place the cubed watermelon in a blender and blend until smooth. Strain the puree through a fine mesh sieve to remove pulp, if desired.

In a mixing bowl, whisk together the heavy cream, granulated sugar, vanilla extract, and a pinch of salt until the sugar is dissolved.

Combine the strained watermelon puree with the creamy mixture and stir until well blended.

Pour the mixture into a freezer-safe container or an ice cream maker. If using an ice cream maker, follow the manufacturer's instructions. If freezing directly, cover the container and freeze for about 4-6 hours, stirring every 30 minutes to prevent ice crystals and achieve a creamy texture.

Once fully frozen and creamy, scoop and serve the watermelon ice cream. Optionally garnish with fresh mint leaves or small watermelon chunks.