JTides is an amazing tide prediction program that is available for free! Visit the Arachnoid site and read more about JTides and other useful Careware programs. Here are some explanatory notes quoted from the JTides site:

"You can choose from any of a large set of US and international tide and current prediction locations, and you can format the results in many ways -- one day (shown), a week, a month, a monthly calendar, even a color month chart (see below). You can also export a database of tidal predictions for any time period, for use with other programs. ... JTides predicts tides and currents using a large database of US and worldwide locations. It graphs its predictions in many useful ways. In comparison tests, JTides' predictions are in good to excellent agreement with a sampling of published and on-line tide tables (but read the caveat below). Also, because JTides contain data for so many sites (over 2000 in the default configuration), you can obtain tidal forecasts for places where there are no printed tables available. And if you want, you can print a calendar of tidal events JTides is a Java MDI (Multi-Document Interface) application -- this means many locations can be graphed at the same time. You may also print prediction charts or export application-portable databases of any size. Because JTides is written in Java, it will run on nearly any computer.

At best, tidal prediction is a chancy business. It relies on field measurements and data collection that can be subject to any of several kinds of errors. Typographical errors, programming errors, and numerous weather and human activity error sources can contribute to a rather large level of predictive uncertainty. Therefore, do not rely solely on the predictions offered by JTides if life or property are at stake.

JTides is a Careware product that reflects the philosophy of Paul Lutus who says:

“Economic principles lie behind many more human activities than most of us realize. We are almost constantly exchanging something for something else. Many economic transactions don't involve money. In traditional societies, and sometimes even [the American] one, people trade using favors, influence, even pure ideas, instead of money. Sometimes money is not the best way to convey value. And sometimes money is so completely inappropriate that it destroys the transaction..." 

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