Activities to do with the coastline and the aquatic environment such as fishing, boating and seaside holidays have been mainstays of the Cornish peninsula for generations. Building on this legacy of marine leisure, this paper explores both the fluidity and materiality of waves, tides and coastal seascapes through a metaphorical framework encompassing symbolic as well as literal issues of pollution and embodiment. It examines Cornwall's distinct surf culture with regard to concerns over the effects of sewage and other malignant discharges on public health and the quality of the seashore environment. Extreme water sports are an increasingly prominent factor in the formulation of Cornish identity. Hence, the paper outlines the ways in which certain environmental pressure groups, charity campaigners and corporate surf companies have become involved in attempts to safeguard the ecological sustainability of coastal leisure pursuits. It does so primarily through ethnographic case studies concerning Surfers Against Sewage, protest-art exhibitions and environmental campaigns. On the surface, the symbolism of fluidity and pollution may appear contradictory. But through an exploration of the materiality of waves, this paper illustrates the dialectical ways in which water and the sea relate to shifting local identities and to creative forms of extreme subversion.