The chapter considers the contribution of the ICJ to the law of the sea, highlighting four areas where the Court has made a key contribution to the development of the law: maritime delimitation cases, the status of islands and rocks, navigational rights in straits and lastly, the conservation of natural resources. The author notes that the Court’s influence is not equal in all of these areas, but emphasises the significant rule that the Court has played in developing the principles and rules of international law applicable to maritime boundary delimitations.