Cook the Shrimp: Heat olive oil in a skillet over medium heat. Season shrimp with garlic powder, paprika, salt, and pepper. Cook shrimp 2–3 minutes per side until pink and opaque. Set aside to cool slightly.
Prepare the Avocado Filling: In a small bowl, combine cucumber, red bell pepper, red onion, lime juice, cilantro, salt, and pepper. Toss gently.
Assemble the Shrimp Boats: Scoop a small amount of avocado flesh from each half to create a cavity. Mix the scooped avocado with the vegetable mixture. Fill each avocado half with the mixture, then top with cooked shrimp. Drizzle optional dressing over the top if desired.