NOAA is amending the regulations for the Florida Keys National Marine Sanctuary (FKNMS or sanctuary) by eliminating the exemption that allows discharges from within the boundary of the sanctuary of biodegradable effluent incidental to vessel use and generated by marine sanitation devices (MSDs) approved under the Clean Water Act (CWA), and by requiring that MSDs be secured to prevent discharges of treated and untreated sewage. This action builds upon the Environmental Protection Agency's creation of a No Discharge Zone (NDZ) for the state waters of the FKNMS, and will help protect the Florida Keys ecosystem from potentially harmful vessel sewage discharges. An environmental assessment has been prepared for this action pursuant to the National Environmental Policy Act. The environmental assessment includes a Finding of No Significant Impact (FONSI) regarding the impacts of this rulemaking.