Wash the fish and shrimp. Peel the shrimp.

Fill a pot with water and bring it to a boil.

Once the water is boiling, add the shrimp and stir for about 5 minutes, since shrimp cooks quickly.

After 5 minutes, remove the shrimp and place it in ice water to stop the cooking. Let it cool, then drain and set aside.

Next, add the fish to the boiling water and cook for about 5 minutes. Remove and let it cool.

Cut the shrimp and fish into small cubes. Add the diced tomato, cilantro, onion, jalapeño, cucumber, and, if you like, avocado. Dice all ingredients.

Once everything is mixed, squeeze the juice from 10 to 12 limes over the mixture. Let it rest for about 5 minutes, then it's ready to serve.