This national management measures guidance for marinas and recreational boating provides guidance to states, territories, authorized tribes, and the public regarding management measures that may be used to reduce nonpoint source pollution from marinas and recreational boating activities. The guidance is intended to provide technical assistance to state program managers and others on the best practicable means of reducing nonpoint source pollution of surface waters from marinas and recreational boating. The guidance provides background information about nonpoint source pollution from marinas and recreational boating-including where it comes from and how it enters the nation's waters-and technical information about how to reduce nonpoint source pollution from marinas and recreational boating. It also discusses the relationship of marinas to the watersheds in which they are located. The guidance can assist marina managers in identifying possible sources of nonpoint source pollution and offers potential solutions. Finding a solution to nonpoint source pollution problems at a marina requires taking into account the site-specific factors that together compose the setting of a marina.