I do not remember but I believe you cannot prebook seats. Windows do not open

We just showed up at the port and booked without any reservations.

The Santa Marira night tour, thanks

Hello. I believe you are referring to the Osaka Cruise Port. If you type that name into your browser it will pull up a guide and area map (Sorry Trip advisor would not let me post the actual link in my response). This is a considerable distance from the port, but the area where the Osaka Water Bus operates is very nice and truly downtown Osaka. Even though it is a distance away, should be easy via train / subway. Based on your length of stay in Osaka and other Japan destinations you may want to work in a little trip on the train / subway as it is famous worldwide for safety and efficiency. If you have not been to Kyoto before, you may want to work a visit in while at Osaka. It is possible to visit both locations if you plan carefully. Please give me a better idea about your cruise and its stop locations / length of stops. I will also try and post the actual transportation route to the Osaka Water Bus from the port in the next couple of days. There are many restaurants around it so it may be a good place to go if your time is limited. I am envious of your visit in October as it is a very good time of the year to visit Japan.