sLACK IS WHEN THE CURRENT TURNS THE OTHER WAY oops caplock
use the canal tide chart to see what time the current turns.
the chart lists the times it changes at the railroad bridge but it's not far off when it changes direction for the east end either unless there is a strong wind with an unusual tide or something.
once the tide turns east, it keeps dropping down for 2 hours.
it's very complicated , as Buzzards bay has 4-5 ft tides that are high no where near the same time as 10 ft. tides from the other end in Cape Cod bay. I'm not sure of the time difference but it is significant.
http://www.nae.usace.army.mil/recrea...ide%202012.pdf
there is the canal chart