We present Riptide, a distributed, cooperative Web caching system. Riptide distributes nodes throughout the infrastructure to serve and manage Web content. Riptide is constructed on the OceanStore distributed storage system and inherits OceanStore's scalability and self-configuration. Nodes may be added or removed as desired. New resources are integrated and begin serving requests automatically; attempts to access unavailable resources are transparently routed to alternative providers. Because the underlying system supports mobile data, copies of content may be moved without expensive directory update protocols. Consequently, the load of serving documents may be quickly redistributed to any of the nodes in the underlying system. We describe the architecture of Riptide and present a preliminary performance evaluation of the implemented system running under a simulated workload.