The tides up the river are different than the bay in that the tide is only flat as a rule for a few minutes, (10-20), unlike the coast where its flat or almost no moving water for more than an hour. The catfish bite well with moving water incoming or outgoing. Not much happens when the tide is slack. Good time to look around for baitballs and structure. Good luck with the catfish. You are coming at my favorite time.
Jason when I was there this week we had some days where there was only two hours of a in or out going tide which I think was due to the wind,and let me tell you it is not easy to ankor a boat with high winds and no current.