Use a knife and cutting board to cut the watermelon into smaller chunks, removing any seeds if present, until you have about 4 cups of pieces.
Add the watermelon chunks to a blender, then pour in 1/2 teaspoon of sea salt for a subtle salty flavor enhancement. Blend on high until the mixture is completely smooth and frothy, about 30-40 seconds.
Place a fine-mesh strainer over a large bowl or pitcher. Pour the blended watermelon through the strainer, pressing gently with a spatula or the back of a spoon to extract as much liquid as possible, leaving pulp behind.
Transfer the strained watermelon juice into glasses. Add ice cubes if desired for extra chill and visual appeal. Serve immediately for optimal freshness and clarity.
Observe the vibrant pink color and clear, watery appearance of the juice. The salt should be subtly perceptible in flavor, and the overall texture should be smooth and crisp on the palate.