Beginning at Pier 6, and routing around the promenades of Pier 5, Pier 3, and Pier 2, continue to the entrance to Pier 1, then run the same route back. You can use the ferry stops at the start and midway points.
Yes, there are restrooms at Pier 6 at Fornino, in the Boathouse in the Pier 5 Uplands, in the orange building on Pier 2, in Empire Stores, in 99 Plymouth, and seasonally at the Pier 1 entrance.
There are water fountains throughout Brooklyn Bridge Park and each has a water bottle filling feature.
Water fountains are turned off for the winter season when outside temperatures reach freezing.