Nantucket was one of the first places in the state to earn federal designation as a no-discharge area. Dave Fronzuto, marine superintendent of Nantucket’s Marine and Coastal Resources Department, is a big advocate for it.

“It makes it a lot simpler. It prohibits the discharge of treated sewage. It is printed on navigational charts,” he said.

The caveat is that the town and the boat basin pump 125,000 to 130,000 gallons a year. “We pump more than anywhere,” Mr. Fronzuto said.

“The problem we have here is that we have mega-yachts,” Mr. Fronzuto said. “We have cruise ships. They are required to seal and lock their system. We inspect them to make sure they are closed. It just makes it so simple. There are state fines that can be $2,000 per incident. We took the step further, we have a bylaw, if you dump sewage, we have a local fine of $300 plus a ban from the harbor. They can be banned from ever using moorings and the harbor.”

Mr. Fronzuto said efforts to get the designation years ago were driven by a desire not only to keep local waters clean, but also to protect the town’s precious shellfish, insuring boat waste was not drifting into shellfish beds.

Nantucket, half the size of the Vineyard, usually produces more bay scallops each winter than any other community in the state.

Nantucket’s designation not only protects the shellfish from raw or treated sewage, it protects against harmful gray water. “There are pathogens in there, Mr. Fronzuto said, “and we were concerned.”

Though large yachts and working vessels may have state-of-the-art treatment facilities onboard, treated sewage may be harmful. Chemicals used in treatment, including chlorine and formaldehyde, can be harmful to sea life. Mr. Fronzuto said he doesn’t want that in his waterways.