Kings Gambit is onto it. I had a diver under our boat yesterday and he said if you sit on the bottom here in Beaufort, there is little or no current. I've read Eldridge and if I could use his example of the Chessy and the approved beers.
The mouth of the bay will be the Bay Bridge, to the north Deltaville, Potomic River, Solomons, Annapolis, and Baltimore in that order. The ocean comes in at the Bay Bridge filling to high tide, fine lets say I'm using a pitcher of beer. Deltaville begins to fill an hour later and the BB is 1 hour after low and I'm now filling both with beer. Next hour later, BB is +2, Delta is +1 and Potomic River is beginning to fill. Next hour BB is + 3, Delta is + 2, Potomic River + 1, and the Solomons beginning to fill. (How we doing, pretty graphic huh).
Next hour BB is +4, Delta +3, PR is +2, Solomons is +1 and Annapolis begins to fill. At hour 5 BB is +5, Delta is +4, PR is +3, Solomons +2, Anna is +1 and Balt is beginning to fill.
So the glasses of beer range from near full at the BB and just starting to fill in Balt. I can only fill them from the Bay Bridge side so the beer (water) is flowing north. As we hit high in the next hour at the BB it now stops rising and begins to fall (someone's drinking the beer). All the places to the north are filling so current is still flowing north.
Next hour BB has gone down to +4, someone begins drinking at Delta, and all the rest are still filling. The current however under the BB should be headed south because we're headed toward an empty glass. Somewhere near these two glasses is where the current is deciding to change its flow direction. That would be slack.
Let's move it ahead so that BB is down to +3, Delta +4, PR is +5, Solomons +4 (still filling), Annapolis +3, and Balt +2. Since the Solomons is now full you might believe slack would be somewhere near, but its not. Its somewhere by the Bay Bridge.
The glass at the Bay Bridge is the largest and consecutively smaller to the one in Balt being the smallest, (concludes the difference in tide range). The slack area should now progress north with the filling of the different glasses.
I've sailed in the rising tide before slack and gotten the boost up the Chessy and it works that way pretty much every time. But along the ICW there are so many inlets and tide differences that slack happens nearer mid tide than at either low or high. The young diver I was talking with said the currents around Morehead City and Beaufort do some strange stuff, but he was unfazed by it. He did admit to not spending any time on a sailboat.
With a tall mast I spend a lot of time planning when to be under the fixed bridges on the ICW and knowing the current flow is a necessity for us. So far we've been entirely outside from the Bahamas, but we're choosing to go inside again instead of around Hatteras. (Old couple and old boat) The bridges were supposed to have been built so they would be 65 feet of clearance at average high tide. Many don't have that amount at low tide as we've experienced over the last six years. Like Jibes was saying, you usually go against the current.
All U Get