Cut fish into small cubes and place in a glass bowl.
Place shrimp into a pan of boiling water. As soon as they turn pink, take them out of the pan, drain and place in a bowl of water and ice cubes. Leave them to cool for 1 to 3 minutes. Drain and add to the fish.
Add the rest of the ingredients: onion, chili, garlic, ginger, salt, pepper, olive oil and cilantro.
Add the lime and lemon juice. Wait 5 minutes, taste, and add more salt if necessary.
You can find the chili pepper called ají limo in Latin grocery stores. However, if you cannot get your hands on it, jalapeño pepper is a good substitute.