Half Tide Rocks are a group of small barren rocks in Massachusetts Bay, located within the city limits of Boston, United States. Massachusetts Bay is one of the large bays of the Atlantic Ocean that form the distinctive shape of the coastline of the U The United States of America —commonly referred to as the The rocks are east of Aldridge Ledge, southeast of Devils Back, southwest of Green Island, northeast of Little Calf Island, and northwest of Calf Island. Aldridge Ledge is a small barren rock located in the South Channel, within the city limits of Boston Massachusetts. Devils Back in Massachusetts, USA is a very small and barren rock in the Atlantic Ocean located within the city limits of Boston. Green Island, also known as North Brewster Island, is a rocky outer Island in the Boston Harbor Islands National Recreation Area, to the north of Calf Little Calf Island is a small rocky Island in the Boston Harbor Islands National Recreation Area, some 9 miles offshore from downtown Boston, Calf Island, also known as Apthorps Island, is a windswept Island situated some offshore of downtown Boston in the Boston Harbor Islands National It borders the northwestern edge of the Hypocrite Channel. The Hypocrite Channel is a small channel in Massachusetts Bay, located within the city limits of Boston.