Mmmmm, ceviche. Ceviche is a citrus-marinated seafood dish, popular mainly in Latin American countries. Both finfish and shellfish are used; finfish is typically used raw while shellfish is usually cooked.
Ceviche is marinated in a citrus-based mixture, with lemons and limes being the most commonly used. In addition to adding flavor, the citric acid causes the proteins in the seafood to become denatured, which pickles or "cooks" the fish without heat. Traditional style ceviche was marinated up to 3 hours. Modern style ceviche usually has a very short marinating period. With the appropriate fish, it can marinate in the time it takes to mix the ingredients, serve, and carry the ceviche to the table.
We had this version in Cozumel. It was wonderful with tortilla chips.