Combine water and 1/4 cup salt in a large saucepan; bring to a boil over high heat. Add shrimp and immediately turn off the heat. Let the shrimp sit until just cooked through, about 3 minutes. Transfer to a cutting board until cool enough to handle, about 10 minutes.Advertisement
Chop the shrimp into 1/2-inch pieces and place in a medium nonreactive bowl (see Tip). Add lemon, lime and orange juice. Stir in cucumber, onion and chiles. Refrigerate for 1 hour.
Stir tomato, avocado, chopped cilantro, oil and 1/4 teaspoon salt into the shrimp mixture. Let stand at room temperature for 30 minutes before serving. Garnish with cilantro leaves, if desired.
Make Ahead Tip: Prepare through Step 2 and refrigerate for up to 4 hours.
Kitchen Tip: A nonreactive bowl or pan--stainless-steel, enamel-coated or glass--is necessary when cooking with acidic foods, such as lemon, to prevent the food from reacting with the pan. Reactive pans, such as aluminum and cast-iron, can impart an off color and/or off flavor.
1/2 fruit, 1 1/2 lean meat, 2 fat