Incoming/Outgoing Tide Question

Hello. Does anyone know how long around the peak or trough of a tide level is there strong current? e.g. current is flowing stronger during the hour right before the high tide or low tide? Or is the rising and lowering of the tide a long and gradual process? Please advise.

Thank you all in advance.

   I think your question is hard to answer because there are too many variables. Most tide books I find have tides and currents, take a good look at that and you'll see what I mean. The golden gate max. ebb and flood relative to the low and high and the slack varies with the different tides. This is an extreme example but it gives you an idea of the answer to your question.
  I always thought it moves the fastest right in the middle of the two tides, and when it gets close to the low or the high it slows down. So for the hour before and after the high or the low it hardly moves at all because it has to change momentum. But once again, is this in Hawaii or Alaska?

Cool. I did a little more googling and found some links with currents as well as tides. Thanks for your reply.

There used to be, and probably still is, a set of current "charts" for the SF Bay put out by Noaa or some other agency.  They are copied into many fancier tide/current books. they show in general terms what to expect at different stages of flood and ebb. They are interesting to look at and hold some surprises.  They are, however, set to some hypothetical "average" set of currents, and also don't take into account fresh water runoff. 
Current "tables" nail it down for the Golden Gate and have a list of adjustments to be made for other locations, including adjustments of time and strength, but these adjustments are not specific to the particular day.