Slack Water

A period when the horizontal tidal current at a particular location is weak or changing direction.

Slack water can occur near the change between flood and ebb, but its time need not coincide with local high or low water because tidal height and horizontal flow respond differently. In rotary tidal streams the current may turn continuously without becoming completely still.

Duration, timing and minimum rate vary with location, springs and neaps, weather and river flow. Predictions should be treated as estimates and distinguished from stand of tide, when water level changes little but current may still be flowing.