Great Bay is a large coastal estuary on the New Hampshire seacoast, covering approximately 5,000 acres and extending 15 miles inland. It is a saltwater bay with 144 miles of shoreline, formed where several rivers meet the sea. Paddling here is fundamentally governed by the tides. During low tide, vast areas of the bay become exposed mud flats, which are impassable and can strand paddlers; planning a trip around high tide is essential. The timing of high and low tide varies significantly from one end of the bay to the other, requiring careful homework. Strong currents are present, particularly during tide changes and notably in the adjacent Piscataqua River. The bay offers a mix of wide-open water and narrower creeks lined with marsh grasses. The shoreline is characterized by forests, fields, and marshes. Motorboat traffic is present, though many operators are respectful of paddlers.

Numerous public launch sites provide access, though many are tide-dependent. Key put-ins include Adams Point, Chapman's Landing, Durham Town Landing, Exeter Town Landing, Jackson Landing, and New Market Town Landing. The Great Bay Discovery Center in Greenland accommodates car-top boats only, with no trailer access. Some sites like Odiorne Point State Park charge a parking fee. A significant portion of the shoreline is privately owned and inaccessible by road, making these designated launches critical. Paddlers can expect to see wildlife such as deer, osprey, great blue herons, egrets, kingfishers, cormorants, ducks, and swallows. Insect repellent is recommended when exploring the smaller creeks. The Great Bay Discovery Center organizes various guided paddling events throughout the summer, including sunset birding tours and full moon paddles, catering to different experience levels.