The Cook Islands Marine Park (CIMP) was claimed to be the largest Marine Protected Area in the world when it was declared in August 2012. This event was part of a trend to develop Large-Scale Marine Protected Areas in the Pacific Islands region and beyond. By some estimates only a few LSMPAs account for most marine biodiversity protection globally. This dissertation represents the first ethnographic account of the development of an LSMPA at local, national, regional, and international scales. An analysis of ethnographic and documentary materials shows that the development of the CIMP is not best understood as a process in which clear goals were set and achieved within existing political and administrative institutions but rather occurred within the context of a political ecology of vagueness, where vagueness is characterized by wandering, the same kind of wandering attributed to vagabonds, sailers, and even the ocean itself. A political ecology of vagueness is analyzed in terms of a flexible conceptual network that approach the vague as a political and social resource. This conceptual framework includes Foucault’s heterotopia, Turners’ notions of liminality as a characteristic of communitas, Fischer’s use of deep play and ethical plateau, and Weber’s characterization of appeals to charismatic authority. An approach to vagueness is presented within a political ecology framework in which ecological distribution conflicts are the result of interstitial social and political processes. It is argued that the the CIMP has become a viable political and ecological project because it was not precisely defined conceptually and because it was collectively imagined and worked upon within social, culture, and political “other” spaces that were interstitial to existing structures.