At Neshaminy in Pennsylvania, the river rises and falls with the ocean’s tides even though it flows another 116 miles to the ocean, and because tides affect this part of the river it is an estuary. This estuary is at sea level and is fresh water rather than salt water, unlike the lower estuary, creating a place where plants and animals from the ocean and from upstream headwaters meet. Estuaries like this were considered important enough for Congress to pass the Coastal Zone Management Act, which provides money to the Commonwealth for proper management of coastal resources. The Delaware Estuary serves as both a river and a link to the ocean, supplies Philadelphia’s drinking water through an inlet pipe three miles downstream at Torresdale, supports boating, provides habitat in the lower estuary for marsh wrens that eat snails and water insects, preserves traces of early Americans who used the river, and contains crabs, shad, and occasionally a stray whale.