Pl. du Panthéon, 75005 Paris, France | You can visit both of your attractions at a time of your choosing during operating hours.
Pantheon Address: Place du Panthéon, 75005 Paris.
The river cruise departs from near the Eiffel Tower at Port de la Bourdonnais, pier 3 (look for the orange pillar). The cruise is operated by Bateaux Parisiens.