If drainage aimed to free land from the vagaries of floodwater, then enclosure was necessary exclude commoners and transfer management of land to improving landlords and tenants. The development of ‘absolute’ private property in early modern England has often been analysed via legal categories or socio-economic outcomes. Resituating property-making as an environmental act, this chapter argues that the contested exercise of land rights in Hatfield Level relied on the ability to determine how water moved, where cattle could graze, and what kind of plants grew. It traces the words and practices through which commoners and improvers defined their rights, often hinging on disputes about the just distribution of resources. This chapter explores a spectrum of local responses to improvement, including complaints of scarcity, socially fraught adaptation, and action to reinforce customary rights. As disputes over enclosure escalated, physical acts of cultivation and grazing became means by rival groups asserted ‘right’ as jurisdiction and legitimacy. In doing so, they created contrasting environments, generative of different social, economic, and political relations.