In 2008, the High Court of Australia handed down its decision in Northern Territory v Arnhem Land Aboriginal Land Trust (‘Blue Mud Bay Case’). The Blue Mud Bay Case affirmed the legal rights of Aboriginal Traditional Owners to control access to the waters of the intertidal zone in the Northern Territory (‘NT’). Immediately after the Blue Mud Bay Case was handed down, an interim amnesty came into operation that was agreed so that nothing changed in practice ‘on the water’. The NT Government and Traditional Owners agreed that the best way to move forward was to negotiate how the intertidal zone would be governed. As at mid-2020 these negotiations are ongoing. Therefore, the Traditional Owners in the NT are not currently controlling access to the waters of the intertidal zone as the Blue Mud Bay Case determined was their legal right.The pre-history and the aftermath of the Blue Mud Bay Case reveals a series of evolving interactions between Indigenous and settler-state assertions of sovereignty in sea country in the NT. This thesis analyses five historical and contemporary episodes: 1) the Woodward Aboriginal Land Rights Commission and the debates about sea country in the enactment of the Aboriginal Land Rights (Northern Territory) Act 1976 (Cth) in the 1970s; 2) the first sea closure hearing and declaration under that legislation in the early 1980s; 3) the High Court’s decision in Commonwealth v Yarmirr recognising native title offshore in 2001; 4) the Blue Mud Bay Case in 2008; and 5) the negotiations between the NT Government and Traditional Owners following the Blue Mud Bay Case. These episodes are analysed using a reconciling sovereignties frame that examines the interaction between co-existing assertions of Indigenous and settler-state sovereignty over sea country. This examination reveals that, although these episodes may appear disjointed, some of these assertions of sovereignty range across all the episodes. Further, the analysis demonstrates that the protracted nature of the Blue Mud Bay negotiations has been caused by the underlying struggle of the settler-state to acknowledge the challenge to the settler-state’s assertions of authority over sea country