In a small bowl, combine vinegar, oil, shallots, mayonnaise, honey, salt and pepper and whisk well until dressing comes together. Set aside.
Using a vegetable peeler, peel cucumber and carrots into long ribbons. Transfer to a large bowl and add tomatoes and watercress. Add dressing and toss lightly to coat well. Serve immediately or refrigerate undressed for up to 1 hour.
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