A stroll along the Seine ... is certainly a wonderful feeling, you can see many monuments, Notre Dame, Eiffel Tower, and other points from another perspective, andn some buildings change from your own point of view. Definitely recommended, it is wonderful afternoon full of varying colors vary and you fall in love.
A different way to see Paris is on the Seine tour Bateau-Mouches, on the boats that make trips around the river doing a route where you can view the most charismatic corners only seen from this river course, another perspective. I would highly recommended!
There is a different way to view and enjoy Paris: sailing the Seine River by boat where you can enjoy wonderful views of the monuments and buildings that line the river. The "Batobus" is a glass-bottom boat to avoid the cold, that is well lit at night and runs every 15-20 minutes. For about 12 euros you can get on and off at each boat stops on its tour of the Seine, just like a bus. It has 8 stops: Tour Eiffel, Musée d'Orsay, Saint Germain des Près, Notre Dame, Jardins de Plantes, Hôtel de Ville, Louvre and Champs Elysées.