 The Back Bay National Wildlife Refuge , established in 1938 , is an 8 @,@ 000 @-@ acre ( 32 km2 ) fresh water refuge that borders the Atlantic Ocean on the east and Back Bay on the west . The barrier islands feature large sand dunes , maritime forests , fresh water marshes , ponds , ocean beach , and large impoundments for wintering wildfowl . It is managed by the U.S. Fish and Wildlife Service . 
