Mill Creek and Old Harbor Creek are the two major sources for water that flows into Sandwich Harbor and out into Cape Cod Bay. There are several other creeks that branch out as well that can be used to further explore the expansive salt marsh. There are also great places to stop and explore by foot. After paddling up and back on the Mill Creek you will have to ride up against the tide until you reach Old Harbor Creek. Once you reach this point the current will be working with you, allowing you to easily paddle up and of the winding streams.