The difference between admiralty and maritime law has historically been that admiralty law was limited to disputes involving torts and contracts on the high seas. Maritime law gradually developed to include all other types of legal disputes that arose on the high seas and other navigable waters. Torts are legal wrongs, and the term "high seas" refers to oceans beyond the territorial jurisdiction of a country. Navigable waters generally are any body of water that functions as a highway for commerce between countries or states. The distinction between admiralty and maritime law faded with time and U.S. courts now use the terms interchangeably.

Admiralty law in the U.S. evolved from England. American colonies initially had vice admiralty courts that derived their authority from England. After the U.S. won its independence, the framers of the U.S. Constitution established that its federal courts would have admiralty and maritime jurisdiction. The U.S. Constitution, however, does not define the terms. Hence, federal courts developed the meaning of the terms over time through various rulings, which blurred any distinction between admiralty and maritime law.

England’s application of admiralty law was confining from the perspective of the U.S. As a result, the U.S. expanded its jurisdiction of admiralty and maritime law. One justification was that the U.S. had inland waters. If the U.S. had adopted England’s narrow application of admiralty jurisdiction, it would have deprived federal courts of jurisdiction of claims arising on its inland waters. This would result in each state asserting its jurisdiction, which would result in numerous bodies of admiralty and maritime law developing and causing confusion.

Federal courts continue have admiralty and maritime jurisdiction in the U.S. This jurisdiction does not preclude states from exercising jurisdiction on admiralty and maritime matters under certain circumstances. The states, however, must apply federal law to disputes involving admiralty and maritime law. This ensures consistency in decisions and allows a uniform body of admiralty and maritime law to evolve, which enables people and companies to act without confusion as to what a jurisdiction may require. The purpose of allowing states to have concurrent jurisdiction is to allow a party to have access to state legal remedies not available under federal law.

Admiralty and maritime law cover numerous categories including charter of parties, charter of goods, law of collision, pilotage, personal injuries, and piracy. To assert its jurisdiction in these areas, a court will take action to arrest a ship. This prevents an owner of a ship from escaping a court’s jurisdiction. The owner will then be required to post a significant bond to recover his ship while a case is pending. This usually is the option preferred to losing a ship that may be worth millions of dollars.