The Fleuve Saint-Laurent (St. Lawrence River) is one of the world's largest river systems, flowing through the heart of Quebec and connecting the Great Lakes to the Atlantic Ocean. It is rich in history and marine life, and its character changes significantly along its length — from a freshwater river near Montreal to a tidal estuary where fresh and salt water meet in the lower reaches around the Bas-Saint-Laurent and Bic regions.

Paddling on the St. Lawrence is considered challenging and can be intimidating even for experienced paddlers, owing to its scale, tidal influences, currents, and exposure. Guides are strongly recommended, particularly for those unfamiliar with the river. Guided sea kayaking excursions operate out of several areas, including Baie de Beauport near Quebec City, where paddlers can take in views of Île d'Orléans, Montmorency Falls, and Old Quebec. In the Charlevoix region, outfitters offer sea kayaking packages and Paddle Canada training along the river's north shore.

Further downstream, Parc national du Bic in the Bas-Saint-Laurent region is well regarded for sea kayaking along its dramatic shoreline of highlands, forests, and rugged coastline. This is the area where the river's fresh water transitions to salt water, and the park is known for its wildlife, including bald eagles.

Near Montreal, Parc du Bassin-de-la-Prairie provides a launch point on the St. Lawrence with boat ramp access. Guided excursions elsewhere on the river typically limit group sizes to maintain safety and environmental standards, and equipment including wetsuits, spray skirts, and mandatory safety gear is generally provided or required. Beginners can participate in guided outings, though independent paddling on the open river demands significant experience and preparation.