Seine river

We bought tickets in the afternoon for a boat ride around the Eiffel Tower later after dark. That way we didn't have to queue in a long line and were able to board right away and got seats with the best views. If you're not able to buy them in advance you can just pick out a boat and buy them prior to departure.

A day trip to Normandy isn't usually recommended since it's a long way and your time to see the sights is quite limited. Spending the night is the best choice. But, if you only have one day it's worth the effort IMHO. You can check Trip Advisor, Normandy forum for more details about where to stay overnight or where to best spend your time on a day trip.

We had planned to take the vedettes du pont neuf cruise when we were in Paris this past June, but unfortunately the boats were not running due to the high waters from all the rain.

When is your trip?

I agree with George in terms of buying your tickets in advance, in order to beat the crowds. You can also buy your tickets online, but we didn't.

Enjoy your time in Paris!

We went on a night cruise 1 hour long. At the Eiffel Tower, walked down the steps to the river and bought our tickets out of a machine. Waited about 30 minutes and then boarded the boat. We chose to sit outside on the upper deck (it was Feb and cold) but we had perfect views.
No reservations needed.

This is something you can do any time without reservations; if the boat is full, take the next one. There are docks at the Eiffel Tower, near Pont d'Alma on the right bank and under Pont Neuf. The routes are all the same although the boats a bit different. Not something to worry about -- do it when it is convenient (and have a warm jacket)

Are these boat tours round trip or one? I am planning on taking one when I go in a few weeks.

Judy - the tours make a roundtrip (circle) up and down the Seine.....you return to your point of departure.