A popular place for ship photography is at The Shore to the west of Gravesend (look on the google map). If you drive down Burch Road from London Road there is car parking space just before the junction with the Shore. Another spot is just to the East of this , if you look on the map it is at Thames way where there is a trading estate with various large retail outlets and the usual parking. The river wall is adjacent to the car park and is opposite Tilbury landing stage. The PLA website gives arrival and departure times, although the arrival times are a little misleading as these are the times at ,for example Sunk pilot and arrival at Gravesend is usually ,I think about 4 hours later . You can also get arrival/departure times for Northfleet Hope Container terminal from
http://www.londoncontainerterminal.com/Vessel_Schedule.asp Obviously there is always tug activity when large vessels arrive / leave
Laurie