Trim the stems of the watercress.
Rinse watercress and dry thoroughly.
Keep chilled until ready to assemble the salad.
2. Combine sherry vinegar, honey, salt and pepper, whisk in olive oil.
3. Assemble salad: Add watermelon, peaches and watercress to a large bowl, dress with vinaigrette, top with pistachio nuts, season with salt and pepper to taste, and serve.