Most people coming to Paris will do the usual Seine cruises - Bateaux and the like. I've done those before and wanted something a bit different. The canal cruise fits that nicely.
If you take the morning cruise from the Quai Anatole Paris (near the Musee d'Orsay) you will get a good part of the usual Seine cruise but then the boat turns into the peaceful Canal St. Martin.it passes through 9 locks, a long tunnel under the Bastille to the Parc de la Villette. It,s quiet, peaceful and with a good commentary (at least until the system broke down on the cruise I was on). Really worth doing.