Make the salad first, so it will be ready to top with the poached shrimp. The salad is most flavorful when made several hours ahead.
Cut the kernels from the cob directly into a large salad bowl
Add remaining vegetables and basil to bowl, but do not toss
Add lime juice, oil and sprinkle with salt
Toss very gently, taking care to coat with dressing while keeping tomatoes and avocado pieces intact
Let sit for at least 15 minutes before serving or cover with plastic wrap and let rest in a cool place for up to 4 hours