Blanch the shrimp in boiling water for 2 minutes until pink and opaque, then immediately transfer to an ice bath to stop the cooking.
Peel and devein the shrimp if necessary, then chop into bite-sized pieces and place in a large glass mixing bowl.
Pour the lime juice over the shrimp, ensuring they are fully submerged, and marinate in the refrigerator for 20 minutes.
While the shrimp marinates, dice the cucumber, tomato, and red onion into uniform small pieces.
Finely mince the jalapeno and chop the fresh cilantro.
Add the diced vegetables, jalapeno, and cilantro to the shrimp bowl.
Sprinkle with chili powder, sea salt, and black pepper, then toss gently to combine the flavors.
Dice the avocado and fold it into the ceviche just before serving to maintain its creamy texture and prevent browning.