High Tide? Low Tide? All you need is a watch and the full moon.

Know the approximate time of high tide without tables.

Captain Shel Miller

Admittedly, where I do most of my sailing you can almost get by without knowing where the tide is at any given time. In southeast Florida the tidal range (difference between high and low tide) is about 24-30”. However, if I’m exploring some skinny (shallow) water area here or anywhere else I definitely want to do so at or around low tide.  That way, if I do run into a sand bar or mud bottom I can throw out an anchor and wait for the tide to come back in to raise the boat off the bottom.

In the Boston area, or other parts of coastal New England the tidal range can easily be as much or more than 12′. That’s a lot of variation between high and low tide which also means some strong tidal currents running between the times of high and low tide, a lot of water coming and going. You certainly want to know where the tide is and whether it’s ebbing or flooding at any given time.

A few ways to know when high tide will occur and whether the tidal current is ebbing or flooding:

  • Standard tide tables you might pick up at your local marina, marine store, or from a local marine publication. These are usually free of charge.
  • Online sources for tide tables including NOAA.
  • Up to date edition of a local cruising guide.
  • An app for your smartphone.
  • Calling a local marina on your cell phone or VHF radio.

If all else fails below is a handy technique I’ve used for years on the east coast of the US where there are  2 high tides and 2 low tides daily.

High tide occurs at about the same time on the full and new moon each month. Knowing that the moon rises approximately 45 minutes later each day we can easily add or subtract that to find the time of high or low tide for any given day. Granted we need to know what day the full moon falls on but this should be pretty easy information to get, or just look up into the sky at night.

Here’s an example: Time of high tide in Ft. Lauderdale, FL on the full moon is within about 30 minutes of 8 am and 8 pm every month during daylight savings (7 am and 7 pm for standard time). So, if today is 4 days after the full moon then high tide will occur at approximately 4 days x 45 minutes/day = 180 minutes or 3 hours later which would be 8 (time of high tide on the full moon) plus 3 hours later gives us 11 am and 11 pm for approximate time of high tide.

You will need to look at some tide tables to determine when the time of high tide is on the full moon for your area. Also, the only area where I have used this technique is the east coast of the US. Your area may differ. But once you know when high tide is on the day of the full moon you’ll be able to depend on this being the case no matter what month it is, just remember to adjust for daylight or standard time and you’re good to go.

Best Sailing,
Captain Shel


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