Wetlands have deep geological histories, stories of bedrock, sediment, and sea rise. But the direction and speed of flow has been shaped just as surely by human interests and intervention. This chapter asks how wetland commons were used, managed, and disputed in the centuries and decades prior to improvement projects. Moving from the action of ice sheets and mosses to national legislation and daily work, it examines how environmental and political scales intersected. By the late sixteenth century, communities in the northern fens faced amplified flood risks and conflict over shared commons. But these challenges did not necessarily strengthen intervention by state-sanctioned institutions capable of coordinating at a larger scale. A less linear and more fragmented picture emerges in the northern fens, where environmental politics pivoted on rights and responsibilities defined by local custom. Fen custom was reproduced by communal decision-making and participatory acts of walking, remembering, and working. It formed a flexible fabric, adapted in response to dynamic waterways and porous boundaries and negotiated through confrontations on riverbanks as well as courtrooms.