Set aside 1 cup (150 g) of the watermelon. Finely dice it and place it in a covered container. Cut off approximately one-quarter of the peeled cucumber, finely dice it, and refrigerate it with the watermelon for serving.

Roughly chop the remaining cucumber, tomatoes, bell pepper, red onion, jalapeno, and garlic. Keep the pieces small enough to fit comfortably beneath the blender lid.

Add the remaining 5 cups (750 g) watermelon, chopped tomatoes, remaining cucumber, bell pepper, red onion, jalapeno, and garlic to a high-speed blender. If the blender is crowded, process the ingredients in two batches and combine them afterward.

Begin blending on low speed, then increase to high. Blend for 1 to 2 minutes, until the mixture looks smooth and no visible vegetable pieces remain.

Add the lime juice, sherry vinegar, olive oil, salt, and black pepper. Blend on high for another 30 to 45 seconds. The gazpacho should look smooth, lightly creamy, and pourable.

If the soup appears unusually thick, blend in 1 to 2 tablespoons (15 to 30 ml) of cold water. Add water only when necessary because watermelon and tomatoes naturally release plenty of liquid.

For an extra-smooth texture, pour the soup through a fine-mesh strainer into a large bowl. Press gently with a spatula, then discard the remaining seeds and skins. Skip this step for a more rustic gazpacho.

Taste the soup before chilling: It should taste slightly more acidic and seasoned than the desired finished result because cold temperatures soften flavor. Add a small splash of lime juice or a pinch of salt only if needed.

Transfer the gazpacho to an airtight container and refrigerate for at least 2 hours. The soup should be completely cold, and the raw onion and garlic flavors should taste softer after chilling.

Stir the chilled gazpacho well because slight separation is normal. Taste once more and adjust the salt, lime juice, or vinegar if necessary.

Ladle the soup into six chilled bowls or glasses. Top each serving with the reserved diced watermelon and cucumber.

Garnish with mint, a light drizzle of olive oil, and thinly sliced jalapeno as desired. Serve immediately while thoroughly chilled.