Defrost the shrimp and shell. Boil in their own liquid until just cooked through, about 3 minutes. Set aside and cool.
While the shrimp is cooling, combine cucumbers, onion, bell pepper, and tomatoes in a serving dish. In a small bowl or measuring cup, whisk together olive oil, vinegar, salt, and pepper. Dress vegetables. Cut cooled shrimp into thirds, add to vegetables, and toss before serving.