Using a sharp chef's knife and cutting board, carefully cut the watermelon into roughly 1-inch cubes and transfer them into the blender container.
Zest the lime using a microplane or fine grater, capturing thin strips of lime peel, then squeeze the juice directly into the blender with the watermelon cubes. Add the pinch of salt.
Secure the lid on the blender and blend on high speed until the mixture is smooth and slightly pulpy, about 30-45 seconds. You should see a uniform, vibrant pink liquid with no large chunks remaining.
Stop the blender and carefully open the lid to check the texture. If desired, briefly blend again to ensure an evenly smooth consistency. Pour the blended watermelon mixture through a fine mesh sieve or strainer into a pouring container to remove excess pulp, if a smoother finish is preferred.
Pour the strained beverage into chilled glasses, optionally garnishing with a lime wedge or a small sprig of fresh herbs. Serve immediately for a refreshing, juicy summer drink.