Ive done the trip on the Waverley from various start points (ipswich, harwich, southwold) heading along the essex coast and up the thames estuary and through tower bridge several times. Very worthwhile and a great day out. It passes fairly close to knock John and within sight of red sands and shivering sands forts and usually goes through tower bridge at around sunset. I cant do it this year because of hols in the lake district otherwise would have done it again.