Duration of Slack Water
(See Chapter 5, Slack Intervals: Nature’s Gift to Mariners)
Correct tidal current time and velocity to your substation (see reference above).
Write down max current speed on each side of your intended transit time. Write
down the time of slack water that falls between the two max current times.
Enter this table in the first column with the higher of the two max current speeds
(round to the closest half knot). Then, slide over to the second column. Write down
the minutes of slack water.
Subtract and add the minutes of slack water to the time of slack water you found
from the tables. The third column shows the total amount of time you have to make
your transit.
Example
You need to find the best time to enter an unfamiliar but well-marked inlet in the
afternoon. The current tables show the following data:
1100 max flood 2.3 knots
1415 slack
1710 max ebb 3.8 knots
Enter the first column below with the maximum speed: 3.8 knots (round to the
nearest half knot): 4.0 knots.
Enter the second column on the same line: 15 minutes. Add and subtract this to
the time of slack water.
1415 – 15 = 1400
1415 + 15 = 1430
Make your transit between 1400 and 1430.
useful tables 303