The concept of territoriality does not appear to fit very well with the limits on state power in admiralty. Territoriality refers to land while admiralty concerns itself with the sea. Limitations on state power on land require adaptation and modification to apply at sea. They must overcome the contrast, pervasive in admiralty, between the law applied on land and the law applied on navigable waters. The adaptation of territorial boundaries to the sea turns out to be a complicated process, which invariably involves multiple boundaries even along the same stretch of coastline. Maritime boundaries are largely unmarked on the fluid surface of the sea, generating multiple ambiguities and controversies. These currently have important implications in the waters ranging from the Arctic Ocean to the South China Sea. Territoriality, whether on land or at sea, has two different components. The first refers to and incorporates measurements on the surface of the Earth, such as the baselines on land that determine zones of maritime control at sea. The second uses location with respect to these measurements as a constraint upon open-ended standards, such as multiple-factor balancing tests, which would otherwise apply regardless of the location of the events relevant to a claim or defense. This Essay explores how these two components of territoriality play out when they go from land to sea.