The Plum Sound Inlet is located about eight miles west of Cape Ann on the Atlantic Ocean behind Plum Island north of Castle Neck. There are not many marine facilities or marinas up Plum Island Sound, but they do exist. There are two marinas on Great Neck near the entrance, and farther up Plum Island Sound at Newbury Old Town, there are three marinas and an anchorage area.
The image above is a view from the west looking east toward the opening of Plum Sound where it empties into Ipswich Bay. Off to the right (south) is the northern tip of Castle Neck, while the southern end of Plum Island can be seen in the upper right (north) portion of the image. Plum Sound breaks off to the left, while the moored boats are located at the mouth of the Ipswich River.
Use NOAA Chart 13274.
From Ipswich Bay, pick up flashing red bell buoy "2" at the mouth of Plum Island Sound (waypoint N42 42.17 W70 44.40), just east of Castle Neck, and then set a course for red nun "8" farther in.
Before you reach red nun buoy 8, you will follow buoys 3, 4, and 6, but you will not find them on your chart. They are not charted as the Plum Island Sound Inlet is constantly shifting and changing course. The Coast Guard regularly moves these marks to reflect the deepest portions of the inlet. If you have any concerns about using the inlet, you may want to use the Newburyport Harbor Inlet about eight miles to the north.