The bar at my home harbour opens four hours a day, and for the first two years I was always on the wrong side of it. Here's what I finally understood.

The window is the tide, not the clock

The channel is only deep enough on the top half of the tide — roughly two hours each side of high water. High water moves fifty minutes later every day, so the window moves with it. Fix the tide, not the time.

Plan backwards from the bar

Once you know the window, the whole passage falls into place: leave early enough to arrive with water under you, and the current does the rest. The bar isn't an obstacle; it's the schedule.