What is slack water?

Slack water is the short, calm period at the turn of the tide, when the tidal current slows to a stop before it reverses. It happens twice between each high and low, once as the flood current fades into high water and again as the ebb fades into low. For a few minutes the water is still, and that stillness is why the app, and this company, is named Slackwater.

When slack water happens

Slack water is tied to the current, not only to the height. In many places it lines up closely with high and low tide, so the high and low times on a tide chart are a good guide to when the water will go still. In bays, inlets, and rivers the current can lag the height by an hour or more, so the slack can arrive well after the printed high or low. Local knowledge and a current station, where one exists, give the precise timing.

Why anglers care

Fish behavior changes with the current. A running tide moves bait and triggers feeding, and the slack at the turn often concentrates fish as the flow eases. Many anglers plan to be on the water through the turn, fishing the last of one current and the first of the next. The calm also makes it easier to anchor, hold a position, or work a specific piece of structure.

Slack water and boating

For boaters, slack water is the safe, comfortable window to pass through a narrow inlet or a tidal race, because the current is weakest. Strong currents against wind or swell stack up steep, dangerous water, and the slack avoids the worst of it. This is one reason a reliable tide app matters most where the signal is weakest.

How Slackwater shows it

Slackwater computes the tide curve on your device from NOAA harmonic data and marks the next high and low, the turning points where slack water occurs. The app reads the rate of change, so it can tell you when the tide is flooding, ebbing, or near slack, and it does this with no signal. Browse tide times by location to see the turns for your spot.