Add the shrimp or prepared tuna in a non-reactive bowl (glass or ceramic) and place in the refrigerator.
In another bowl non-reactive bowl, prepare and combine the onion, peppers, avocado, and 3 Tablespoons of the lime juice. Gently toss together these ingredients together.
Add the shrimp or tuna that was set aside in the refrigerator to the mixture and top with the remaining lime juice and extra virgin olive oil. Toss all ingredients together. Season with salt and pepper. Cover and refrigerate 30-60 minutes. Stir it gently once or twice to bring flavors together.
When you are ready to serve top with the fresh chopped cilantro and stir. Place in a decorative serving bowl and serve with tortilla chips.