Navigation General · Currents
In a tidal estuary, slack water (zero current) typically occurs:
- AExactly at the time of high and low tide
- BApproximately midway between high and low tide
- CShortly before or after the time of high and low tide, but not necessarily at the same time✓ Correct
- DOnly at the entrance to the estuary, never inside
Explanation
In most tidal waterways, slack water (current reversal) is offset from the time of high or low tide by a variable amount — often 1 to 3 hours. The offset depends on channel geometry, freshwater input, and local bathymetry. Tide tables and current tables provide separate predictions for each.
Authority: NOAA Tide Tables
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