Folks cruising the PNW often use a yearly publication, Ports and Passes, to plan for transiting areas with swift currents, etc. It gives the times for slack water in relation to tide reversals. And they do not directly coincide much of the time. If it’s critical to transit an area during slack water, one had better consult the proper reference. In the PNW it might also be a matter of decision to transit during slack associated with the flood tide reversing, or slack associated with the ebb tide reversing. The latter is usually preferred. Up there, currents associated with a flooding tide are swifter than those associated with an ebbing tide in the same location. So, near the “bottom” of the ebbing tide currents are at their slowest.