There are many different ways to cross a river, but the nicest is of course by boat. Between the Watertorenhaven on the North side and the Piekstraat on the South side of the Maas you can take Lijn 19 (Line number 19) a small ferry boat and a branch of the Waterbus. It takes you from the Esch to Feyenoord, a very short trip, just to cross the water and you can take your bicycle along with you for free. Especially nice when the weather is fine. You have a beautiful view from the water of the Van Brienenoord bridge and of the skyline of Rotterdam.
In the old days there were a lot of ferries ferrying across rivers in the Netherlands and this is a relatively new one. Not for tourists but for people who work on the other side of the river from where they live. That is the only drawback of this ferry line. It only services on weekdays during business hours, from 07:00 until 19:00.