Prepare the shrimp by peeling, deveining, and chopping into bite-sized pieces if they are large.
Briefly blanch the shrimp in boiling water for 2 minutes until pink and opaque, then immediately plunge into an ice bath to stop the cooking.
In a large glass bowl, whisk together the lime juice, extra virgin olive oil, sea salt, and black pepper.
Add the cooled shrimp, diced cucumber, finely diced red onion, diced tomato, and minced jalapeño to the bowl, tossing gently to coat.
Cover and refrigerate for at least 30 minutes to allow the citrus to infuse the shrimp with bright, zesty flavor.
Just before serving, gently fold in the diced avocado and fresh chopped cilantro to maintain their texture and color.