Great Bay is a large, tidal saltwater estuary on the New Hampshire seacoast, covering approximately 5,000 acres with about 150 miles of shoreline. It extends 15 miles inland and is fed by seven rivers. Paddling here is fundamentally governed by the tides. Vast areas of the bay drain during low tide, exposing extensive mud flats that are impassable on foot and can strand paddlers. The timing of high and low tide varies significantly from one end of the bay to the other, requiring careful planning for any trip. Strong currents are present during tide changes, particularly noted in the Piscataqua River and near Hilton State Park. Many access points are tide-dependent, meaning their ramps or launches may be unusable at low water. Primary launch sites include Adams Point, Cedar Point, Chapman's Landing, Durham Town Landing, Exeter Town Landing, the Little Harbor/Back Channel, Hilton State Park, Jackson Landing, New Market Town Landing, Pierce Island in Portsmouth, Odiorne Point State Park in Rye, and Sandy Point. The Great Bay Discovery Center in Greenland offers a car-top boat launch. Fees may apply at some sites like Odiorne Point State Park and Pierce Island. The shoreline is largely privately owned and inaccessible by road, making these designated launches essential.

The paddling environment features wide, open water bordered by forests, fields, and marsh grasses. Motorboat traffic is present, with most operators reported as respectful. Paddlers can explore side creeks lined with marsh grasses, though these may be obstructed by debris like downed trees. Insect repellent is recommended for these areas. Wildlife sightings commonly include osprey, great blue heron, egret, kingfisher, cormorants, ducks, swallows, and occasional deer. The aesthetic is a mix of expansive bay views and more intimate, winding waterways. The Great Bay Discovery Center organizes guided paddling events for various skill levels, including sunset birding tours, full moon paddles, and stand-up paddleboard instruction, though independent paddling is common. The area is part of the National Estuarine Research Reserve system, underscoring its ecological significance.