How to Make It
In a blender, puree the cucumbers with the sugar, rice vinegar and salt. Strain the puree through a fine sieve set over a medium bowl. Refrigerate the cucumber water until chilled.
In a large bowl, toss the red and yellow watermelon with the tomatoes, cucumber, shallots, extra-virgin olive oil, lemon juice and tarragon. Cover and refrigerate for at least 2 hours and for up to 6 hours.
Shortly before serving, light a grill or heat a grill pan. In a large bowl, toss the shrimp with the pure olive oil and season with salt and pepper. Grill the shrimp over high heat until browned and just cooked, about 3 minutes per side.
Spoon the watermelon salad into 4 shallow bowls. Arrange the grilled shrimp on top. Ladle the cucumber water into each bowl, top with the baby salad greens and serve.