This bill makes permanent a temporary exemption from permit requirements of the National Pollutant Discharge Elimination System (NPDES) under the Federal Water Pollution Control Act (commonly known as the Clean Water Act). The exemption applies to a vessel that is less than 79 feet in length or a fishing vessel for any discharge: (1) of effluent from properly functioning marine engines; (2) of laundry, shower, and galley sink wastes; or (3) that is incidental to the normal operation of those vessels. Under current law, the exemption is scheduled to end on December 18, 2017. This exemption does not apply to garbage discharged overboard, other discharges when the vessel is operating in a capacity other than as a means of transportation, discharges of ballast water held in ships to increase stability, or any discharge that contributes to a violation of a water quality standard or poses an unacceptable risk to human health or the environment.