A more thorough explanation:

The locality test is a requirement in maritime law that states for a federal court to have jurisdiction over an admiralty tort case, the alleged wrong must have occurred on navigable waters.

For example, if a person is injured while on a boat in a navigable waterway, a federal court may have jurisdiction over the case under admiralty law because the injury occurred on navigable waters.

However, the locality test was replaced by the locality-plus test in 1972. The locality-plus test requires not only that the alleged wrong occur on navigable waters but also that it relates to a traditional maritime activity. This means that the case must have a significant connection to maritime commerce or navigation.

For example, if a person is injured while working on a ship that is transporting goods between ports, the case may have a significant connection to maritime commerce and navigation, and a federal court may have jurisdiction under admiralty law.

Overall, the locality test and the locality-plus test are important requirements in determining whether a federal court has jurisdiction over an admiralty tort case.