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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. Jun 9 '16 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. – Todd Wilcox Jun 9 '16 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 Jun 9 '16 at 21:26
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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.

  • and also for having precise measurements of time and amplitude – njzk2 Jun 9 '16 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. – Greg Hewgill Jun 9 '16 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. – whatsisname Jun 9 '16 at 5:41
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    @whatsisname Locals would be well-aware of that. – gerrit Jun 9 '16 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? – whatsisname Jun 9 '16 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 guess work, but if you have to harbor you 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 weeks 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 height difference in water height could be "a gap big enough to sandbag an area". Not specifically tied to boating but important none the less.

  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 your in local waters your 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 loose track of time, and thus get surprised (or stuck) because of that, then because you didn't know about the tides.

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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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