At the back of Amsterdam Central Station you can find the ferries to Amsterdam North. They are only accessible for pedestrians and bicycles and people use them a lot. A short movie showing just how many bicycles cross the water to get from and to Amsterdam North on a Friday afternoon in February 2010.
The Amsterday bicycle ferries
BICYCLE DUTCH 
We used these to get across to the film museum last year – really easy and quick and full of bikes!