The oceans are extremely important part of the identity of Cape Cod National Seashore, after all, "sea"shore is part of our name. From the expansive tidal flats of Cape Cod Bay, to the pounding storm-driven swells of the Atlantic Ocean, these salty ocean waters influence almost every aspect of life on Cape Cod. The NPS manages a quarter-mile of ocean from the seaward edge of the average low-tide line. Commonly within this quarter-mile of ocean, seal colonies, seabirds, and other marine life (including whales, on occasion) are making use of seasonally available, rich food resources. Near-shore and surrounding Cape Cod waters are part of the Northwest Atlantic Ocean, Gulf of Maine ecosystem, which is highly productive in the south thanks, in-part, to the up-welling of nutrient rich waters from Stellwagen and Georges Banks.
Endangered North Atlantic right whales and humpback whales visit Cape Cod waters during the spring and early summer. Right whales rely on critical habitat areas in Cape Cod Bay, Stellwagen Bank, and the Great South Channel area to the east of Cape Cod for feeding and nursery grounds. Visitors can see whales from Cape Cod beaches, especially on clear days during the spring season and near Race Point. Seal populations in the Northwest Atlantic have recovered since establishment of the Marine Mammal Protection Act in 1972. Sometimes dense colonies of gray and harbor seals can be seen in summer months within and near the seashore, including High Head and South Chatham/Monomoy beaches. Dolphins, sharks, and commercially important fish, such as striped bass and bluefish, also make use of the nearby, seasonally productive ocean environment. In addition to abundant marine life, the ocean surrounding Cape Cod is rich with maritime history. Numerous shipwrecks are scattered throughout inland waters, some dating back to the 18th century.