Currents and tides are not the same things, although marine and estuarine underwater topography may marry the 2 in a difficult matrimony.

In northern New England, our diurnal tidal difference is 11-18 feet of water. Each tide, in total , roughly 12 hrs. That is from fully high, through low, back to full high. Slack tide is roughly 20 minutes ( more or less depending on where you actually are). Scallop and urchin divers seem to get their quotas every day they are allowed, and their quotas take a heckuva lot longer than 40-60 minutes out of 12 hours.

BVI tide table ( one tide daily) for today indicates that low tide was at 8:23 this morning, High tide will be at 11pm this evening, and the tidal difference is about .14 m, which is less than 6 inches over @15.5 hours.

I think my idea of slack tide is far far different than when referring to the BVI tides.