Plum Island Sound
Plum Island Sound begins about one mile east of the Rt. 1a bridge over the Parker River. The river turns south and broadens out into a large estuary behind the barrier beach island called Plum Island. The Sound runs for about 4 and 1/2 miles until it joins up with the Ipswich River and empties into the Atlantic Ocean between Plum Island and Castle Neck. Most of the Sound is surrounded by the Parker River National Wildlife Refuge and is also part of the Parker River/Essex Bay Area of Critical Environmental Concern.