If using raw shrimp, peel, devein, and blanch them in boiling water for 2 minutes until pink, then immediately plunge into an ice bath to stop the cooking.
Chop the chilled shrimp into bite-sized pieces and place them in a large glass or ceramic bowl.
Pour the lime juice, lemon juice, and orange juice over the shrimp, ensuring they are fully submerged, and let marinate in the refrigerator for 20 minutes.
While the shrimp marinates, finely dice the red onion, cucumber, and tomato, and mince the jalapeño after removing the seeds.
Remove the shrimp from the refrigerator and stir in the diced onion, cucumber, tomato, jalapeño, and chopped cilantro.
Gently fold in the diced avocado, being careful not to mash it, and season the mixture with sea salt and black pepper.
Serve immediately in chilled bowls or over a bed of crisp greens for a complete, clean-eating meal.