The Pilot Boats operate out of Harwich but are seen in the waters of the Stour Estuary of which half is in the County of Suffolk, these transport Ships Pilots out to and from large vessels in the shipping channels in the North Sea.
Details of the Pilotage from Harwich can be viewed here http://www.portoffelixstowe.co.uk/PUBLICATIONS/JOURNAL/frmmarine.aspx
Pilot Launch New and Old by johncooper of suffolk, on Flickr
Pilot boat approaching mv Balmoral in the mouth of Harwich Haven to pick up the pilot from Ipswich c1998