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People have put a lot of work into predicting tides. To a local, who knows the conditions of a certain area, are tide tables really necessary? How surprising are the tides ever going to be to someone who's been sailing the same bay for decades?

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    I don't have a tide chart. I'm never surprised by the tides. When I go sailing, I might think "Hey, it's low tide". But I'm not surprised.
    – WW.
    Commented Jun 9, 2016 at 2:41
  • Even non-locals who know about tides are not surprised. As Greg writes in his answer - they follow a predictable pattern. I usually spend two weeks at the beach every summer and basically after the first low/high tide on the first day, I'm calibrated and I know approximately when the next low/high point is and when the best time to go in the water is, etc. Usually the first afternoon I'm planning lunch time the next day around water time based on tides and weather. Commented Jun 9, 2016 at 12:27
  • @ToddWilcox Some places have a 5 ft tide and some have a 25 ft. and that can be surprising as a vacationer. But you do learn fast.
    – Brad
    Commented Jun 9, 2016 at 21:26
  • There are a few exceptions where tide-charts (or apps) are really essential. The North Sea is quite famous for mudflat hiking. When you plan to walk from one island to the next, then you must not hit the rising water. Commented Jun 5, 2023 at 7:34

3 Answers 3

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Tides are generally not surprising - they do not change much in amplitude from one day to the next, and the peaks happen slightly less than an hour later each day.

The amplitude of the tides mostly follows the phase of the moon. The highest tides happen on the full moon and the new moon, with slack tides in between.

Tide tables are useful for predicting what the tides will be months or even years in the future.

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  • and also for having precise measurements of time and amplitude
    – njzk2
    Commented Jun 9, 2016 at 2:19
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    @njzk2: Good point, they can be used to accurately predict flooding events if you know at what height flooding starts. Commented Jun 9, 2016 at 2:29
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    While this is true for most places, there are places with very non-obvious tide patterns dye to coast geometry, e.g. the cook strait and nearby waters in the Marlborough sounds. Commented Jun 9, 2016 at 5:41
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    @whatsisname Locals would be well-aware of that.
    – gerrit
    Commented Jun 9, 2016 at 10:15
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    @gerrit: they'd know that they can be unpredictable, but for most locals, thats about it. They wouldn't be able to tell you the times and behaviors off the top of their head. Even the ferry ship captains are sometimes caught off guard by the tidal flows. How would some random dude know better? Commented Jun 9, 2016 at 14:59
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As someone that lives, works, and plays in a coastal area in Florida, I can say that I qualify as a local. The answer is nearly never. You would hardly ever be surprised by the tide. It becomes a lot like being surprised by the position of the sun. You may, on occasion notice it's later then you thought it was, but the "fact" that it's later isn't a big surprise. Tides are the same way. They don't shift around much day to day. So you may get taken off guard when you spend 8 hours doing a 2 hour task, but the fact that the tide has changed isn't really a surprise.

Now I say "nearly never" because there are three important times that I can think of where the need to be precise is so important that the water height at a given time can actually be surprising:

  1. Storm (hurricane) conditions. Knowing when high tide is in combination with the storm's route can help you choose a better place to harbor your boat. Of course it's all guesswork, but if you have to harbor your boat in a storm, then being able to guess where can be important. The other side to this is that the answer is almost always Boat no go in storm, move boat out of storm path and with a week's worth or more of warning time, it's really not that hard to do.

  2. Flood Conditions. After a storm, predicting flood conditions can be useful. Specially if you're in an area along an estuary. The difference in water height could be "a gap big enough to sandbag an area". Not specifically tied to boating but important nonetheless.

  3. Areas that are impassable. There are a few areas that getting even a small boat in or out requires you do so at high tide. The small difference in draft can make the difference between bottoming out and a smooth trip. Usually if you use one of these places you know, (though I see a ton of people get stuck because they "follow the guy on front of them" without realizing his boat is sitting higher.) and it's not like the range is only a few moments. Usually it's a few hours on both sides of high tide.

So essentially, a tide table is mostly useless in local waters (for locals). Having a general idea about when high or low tide is - is useful, but you can almost always get that off the radio/TV/internet/whatever. If you're in local waters you're not likely to be surprised by the tide because it either doesn't matter, or it matters so much that your entire trip is planned around it. It's more likely you lose track of time, and thus get surprised (or stuck) because of that, than because you didn't know about the tides.

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  • I does depend on your definition of "local" though. Someone living just far enough inland to not see the sea all week would quite likely want to know before going to the beach at the weekend. Then you either need a table or to work out the daily drift from last weekend properly - or get caught out. It's not just boaters - some beaches are much better/safer at certain states of tide, and birdwatching at the coast is often heavily tide-dependent (e.g. on a rising tide wading birds will be getting closer to where you might watch from)
    – Chris H
    Commented Jun 6, 2023 at 20:35
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As other have said, tides should not be surprising to locals, which makes sense as tide tables are not designed to be used by locals. They are intended for people a) to whom tides are important, that b) are not familiar with the local tides, and that c) intended to visit at some point in the future. Unless all three conditions apply, tide tables will be of little or no interest.

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