California No Discharge Zones

What does a no discharge zone mean? 

Discharging raw sewage into any of California’s lakes, rivers, reservoirs or coastal waters within three miles of shore is prohibited within U.S. navigable waters. State law also prohibits dumping any human waste (treated or untreated) in a marina, yacht harbor, fresh water lake, or fresh water impoundment from any vessel tied to any dock, slip or wharf that has toilet facilities available for the use of people on the vessel.