The current typical of rivers, estuaries, inlets and narrow channels, where the shoreline forces the flow back and forth along one axis. Each cycle runs flood, slack, ebb, slack, and current tables give times of slack and maximum flood and ebb. Speed changes roughly sinusoidally between slacks, which is why the strongest flow sits about midway between them.
It's a reversing current through the inlet, so either you go at slack or you go with it.
Also heard as
- rectilinear current
- reversing tidal current
Do not mix it up with
- Rotary current: A rotary current turns through every compass direction without true slack; a reversing current goes back and forth along one line.
Related terms
Rotary current
An offshore tidal current whose direction keeps swinging round the whole compass during each tidal cycle.
Slack water
The short lull when a reversing current almost stops while it swaps between flood and ebb.
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.