The moment of minimum current when a reversing current turns. Slack may last a few minutes or most of an hour depending on the place, and it rarely coincides with high or low water, because in a progressive tide wave the strongest current flows near high and low water and slack falls between. Divers, tows, pilots and salvage crews schedule critical work around predicted slack.
Slack water at the pass is 1342, get the divers down at 1330 and out by 1400.
Slack predictions assume average river flow; a strong freshet can shorten or wipe out the slack before flood entirely.
Also heard as
- slack
- slack tide
- slack before flood
- slack before ebb
- dead slack
Do not mix it up with
- Stand: Stand describes the water level holding still; slack describes the current stopping.
Related terms
Flood
Tidal current running in from the sea and up rivers and estuaries, mostly while the water is rising.
Ebb
Tidal current running out toward the sea and down rivers and estuaries, mostly while the water is falling.
Stand
The pause at the top or bottom of the tide, when the level hangs nearly still before turning.
Reversing current
A tidal current that runs back and forth along one line, flood one way and ebb the other, with slack at each change.
Tidal current
The horizontal flow of water that accompanies the rise and fall of the tide.