Marinate fish in lime juice for 4 to 5 hours, until fish turnswhite. Mix fish with the juice with all other ingredients. Serve chilled.
Note from Alexis:Ceviche is not Mexican, it's Ibero-American. It's also consumed in Spain and Southern France and there is even a variant in the Philippines (as a Spanish import). The Japanese love it too. For example, Nobu, the famed NYC & London Japanese food restaurant carries it. Peruvians are perhaps best known for taking Ceviche to an art form (quality, variety, presentation) and as a national symbol. There are over 20 varieties of Ceviche in Peru alone. From the humble Seabass (corvina) to Mixto (varied seafood ingredients, all marinated in lime, which they call 'limon'), to Ceviche de Paiche, a Sturgeon-like fish that lives in the Amazon river basin. Chileans and Ecuatorians also take pride in their many varieties and their Ceviche-making tradition.