The terms international waters or transboundary waters apply where any of the following types of bodies of water transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed regional seas and estuaries, rivers, lakes, groundwater systems (aquifers), and wetlands.

Piracy is an act of robbery or criminal violence by ship or boat-borne attackers upon another ship or a coastal area, typically with the goal of stealing cargo and other valuable goods. Those who conduct acts of piracy are called pirates, and vessels used for piracy are called pirate ships. The earliest documented instances of piracy were in the 14th century BC, when the Sea Peoples, a group of ocean raiders, attacked the ships of the Aegean and Mediterranean civilisations. Narrow channels which funnel shipping into predictable routes have long created opportunities for piracy, as well as for privateering and commerce raiding.