Most of the Piscataqua River is rough to kayak.  What people see is the fast current with eddies that could overturn all but the most experience kayaker.  There are some places for novice like myself.  Here are some of the internet locations.

http://driftwoodkayak.net/trips/piscataqua-river/

http://www.10best.com/destinations/maine/portland/york/attractions/piscataqua-river-kayaking/

http://www.nileguide.com/destination/portland-maine/things-to-do/chauncey-creek-kayaking/1668697