I think you want to look at the current (water flow) as opposed to tide (water height). My current prediction program shows the following for September 4 , 2008 at Hells Gate.
Slack Water Before Ebb: 1:47 AM
Max Ebb: 4:28 AM Direction 230 Deg 4.4 kt
Slack Water Before Flood: 7:50 AM,
Max...