Marion is located on Buzzards Bay, and its geography is shaped by the water. Much of the town is separated into two halves by Sippican Harbor, with Converse Point to the west and Sippican Neck to the east. To the west of Converse Point is Aucoot Cove, where Aucoot Creek and Borden's Brook empty into the bay. Sprague's Cove, Hammetts Cove (which is directly east of Little Neck), Blankenship Cove and Planting Island Cove are all coves off of Sippican Harbor. To the east of Sippican Neck is Wings Cove, which separates the neck from Great Hill Point. Along the northeastern border of town is the Weweantic River, which separates the town from Wareham.