To make ceviche, small cubes or slivers of fish or shellfish are submerged in citrus juice, often with chili peppers or other seasonings, until the marinade changes the appearance and texture of the fish much the same way that heat would. But there is no cooking, so the dish tastes wonderfully refreshing. Scallops are the safest shellfish to eat raw because they do not filter seawater like other shellfish, such as oysters.