Admiralty law or maritime law is the distinct body of law (both substantive and procedural) governing navigation and shipping. Topics associated with this field in legal reference works may include: shipping; navigation; waters; commerce; seamen; towage; wharves, piers, and docks; insurance; maritime liens; canals; and recreation. Piracy (ship hijacking) is also an aspect of admiralty. 

The courts and Congress seek to create a uniform body of admiralty law both nationally and internationally in order to facilitate commerce. The federal courts derive their exclusive jurisdiction over this field from the Judiciary Act of 1789 and from Article III, § 2 of the U.S. Constitution. Congress regulates admiralty partially through the Commerce Clause. American admiralty law formerly applied only to American tidal waters. It now extends to any waters navigable within the United States for interstate or foreign commerce. In such waters admiralty jurisdiction includes maritime matters not involving interstate commerce, including recreational boating. 

Regulations are found in the Federal Rules of Civil Procedure.  The Supplemental Admiralty Rules take precedence over the Federal Rules of Civil Procedure in the event of conflict between the two.   Source: http://www.law.cornell.edu/topics/admiralty.html

USMS District of Columbia Superior Court does not conduct the agency’s function for Admiralty for this courthouse.