Having passed through the Cape Cod Canal one time against the current – and if you are wise, you will do it only once – we learned it is well worth planning our trips to travel with the current, or at the least to go at slack current. The savings in time and fuel, especially at today's prices, can be significant.
Another good example of where knowing the speed and direction of the current is critical is Hell Gate in New York City. With currents that run as fast as 5 knots, not only can you waste fuel and time if you try to run against the current, it can be downright dangerous if you are running with the current and meet one of the many barges coming through the infamous blind S-curve.
cTide is a program for Windows Mobile that provides reliable data from about 5,900 locations, including Boston (above) and Cape Cod Canal (below). 
The speed and direction of the current can also be critical information when docking. Not only is it important to know the direction, so that you can safely come in against the current, at some docks it can be vital to know the current strength. In areas with extremely fast currents you may want to time your arrival and departure accordingly.
We learned this lesson the hard way the first time we pulled out of a slip in St. Augustine, Florida. The current at our home dock can regularly be 1 or 2 knots, so we felt pretty comfortable docking with the current running. We knew the tides in St. Augustine were a "middling" 5 feet, but we failed to take into account the effect of the nearby ocean inlet. Fortunately, the only damage was a bent anchor when we were forced against a piling.
Having a program readily at hand to check tidal information has become a requirement on the Intracoastal Waterway. We have found that the lack of funding for dredging on the Atlantic ICW has taken a toll. Boaters can no longer depend on 12 feet of controlled depth down its length. For many boats, transiting the Atlantic ICW is an exercise in timing when transiting low areas.
A few years ago, we were in Beaufort, South Carolina hoping to meet friends in Charleston. This is a portion of the ICW we had avoided in the past. Weather predictions were poor and remained so for several days. We decided to see if we could "ride the tide" up the ICW. Using tide predictions, we were able to time our trip by varying our speed to match high tide at 8 different tide stations. We had charts and diagrams indicating the precise timing for the various stations, which were checked off as we progressed. We're pretty sure that less planning went into the last Space Shuttle mission. We were successful, and while it was an interesting exercise and a good test of our tools, we're not too eager to do it again.
CTIDE AND NAVSTATION TIDES
cTide is a free, graphical tide prediction program for Windows Mobile. It is also based on XTide and provides predictions for about 5,900 locations around the world. Data can be displayed in a graphical form, and predictions are available on any date between 1970 and 2038. We have found cTide to run slower than Tide Tool but the predictions are reliable and the display is comparable. (To download a free copy and access additional information, see link.)
NavStation Tides is a Windows Mobile program that offers tide predictions for more than 3,000 stations worldwide, using the UK Admiralty Simple Harmonic Method. The software costs $40 and includes tidal data for two calendar years, with additional years available for a small fee. Tide predictions can be displayed as a table or using a tide plot. Another commercial application is Tide Plotter, which offers a wide variety of display formats including plots, tabular and map-based. Tide Plotter sells for about $22, which includes software versions for your Windows CE, Windows Mobile or Pocket PC smartphone, as well as your PC.
To access tide predictions on your Apple iPhone there is Tide App, a web-based tide predictor. With Tide App you can obtain a five day tide prediction table starting with the current date for a variety of locations in the U.S., the U.K., Germany and parts of Canada. It can also provide a static graphical display of the tide cycle. Its main limitation is that you cannot change the start date for the tide predictions. Like other programs, predictions are based on XTide.
To access tide and current predictions on a Blackberry or Symbian smartphone you will need to go to one of the many available websites. The NOAA website offers a wealth of information including interactive maps, tide plots and text-based tide charts, which you can configure in a variety of ways by selecting the units, time zone and past and future date ranges. It is not formatted for display on smartphones, so it can be somewhat cumbersome to use.
WEB-BASED APPLICATIONS
There are a variety of web-based servers using XTide to serve tide predictions online. One of the most used is a website from the University of South Carolina (see link). The site provides an almost overwhelming number of options for displaying tide and current predictions. The tide table displays fine on a smartphone. Most of the rest of the website is cumbersome to use. But it's a good option in a pinch.
