Maritime law is the set of rules that govern what happens on the open sea and in navigable waters. These laws help clear up issues that might arise and ensure people or organizations who work on the water behave properly and are protected.

Traditionally, maritime law has dealt with charter parties and contracts, cargo, collisions, liens, demurrage, forfeitures, general averages, salvage rights, personal injuries and torts, seamen’s wages and maritime insurance. More recently, recreational boats (including speedboats and sailboats) have been brought within its jurisdiction, as well as offshore platforms and jackup rigs. Moreover, the law also addresses shore-based workers who may be injured in the course of disembarking and embarking ships, as well as during excursions to the shore.

A central concept of maritime law is that of admiralty jurisdiction, which is based on federal law and is broad and comprehensive. Its sources include the Constitution’s article III — which gives courts power to hear admiralty cases — and an ancient legal principle known as “ius gentium,” meaning the law of nations. This principle establishes that a ship’s master and owners have a duty to render aid to anyone in distress at sea. It is codified in international treaties such as the United Nations Convention on the Law of the Sea, 1982 and in IMO instruments including the International Convention for the Safety of Life at Sea, 1974.

The Supreme Court has held that admiralty and maritime jurisdiction includes all public navigable rivers, lakes and other bodies of water in the United States where there is a commercial nexus. But, the Court has also ruled that an ordinary mortgage securing a ship or its equipment does not constitute a maritime lien and cannot be enforced in admiralty.