A partly enclosed coastal body of water in which river water is mixed with seawater is called an estuary. An estuary is thus defined by salinity rather than geography. Many coastal features designated by other names are in fact estuaries (for instance, Chesapeake Bay). Some of the oldest continuous civilizations have flourished in estuarine environments (for example, the Tigris and Euphrates rivers, the Nile delta, and the Ganges delta).
âFederal crimesâ refer specifically to offenses that violate U.S. federal laws. They are investigated by federal law enforcement and prosecuted by United States attorneys in federal courts with federal judges.
Mail fraud which crosses state lines or involves the (national) United States Postal Service is a federal offense. An equivalent offense, under Canadian criminal law, is theft from mail (section 356 of the country's Criminal Code).