Shrimp Ceviche

Name: Shrimp Ceviche
Ingredients: 3 pounds large raw tiger shrimp, peeled and deveined; 4 large tomatoes, seeded and diced; 1 small red onion, diced; 2 serrano peppers, seeded and finely chopped; 1 cucumber, peeled and diced; Handful cilantro, chopped plus several sprigs for garnish; 2 avocados, peeled, pitted and cubed; 1 teaspoon olive oil; Salt to taste; Pepper to taste; 6 limes, juiced; 4 lemons juiced; 1 bag of tortilla chips or tostadas