Bring a pot of salted water to a boil and blanch the peeled shrimp for 2 minutes until pink, then immediately plunge them into an ice bath to stop the cooking.
Drain the shrimp thoroughly and chop them into bite-sized pieces, then place them in a large glass mixing bowl.
Pour the lime juice, lemon juice, and orange juice over the shrimp and let the mixture marinate in the refrigerator for 15 minutes.
While the shrimp marinates, dice the cucumber, red onion, and tomato into uniform pieces and finely chop the fresh cilantro.
Gently fold the diced avocado, cucumber, red onion, tomato, and cilantro into the shrimp mixture.
Drizzle the extra virgin olive oil over the ceviche and season with sea salt, black pepper, and a pinch of red pepper flakes.
Toss everything lightly to combine, ensuring the avocado remains creamy and intact, and serve immediately while chilled.