That might sound trite, but even though the Tide-Mate has only two buttons to press, it does require a bit of getting used to. Once you understand the logic of the system, though, it coughs up the results almost instantly. We were a little disturbed at first that the predictions the Tide-Mate gave for some of the Standard ports did not entirely match those of two major nautical almanacs. Some times may at first seem slightly different from those in the almanac. This is usually where the range is smallest and the stand is longest.
Some ports have stands of up to two hours.
Then it is extremely difficult for anyone to say when the actual time of high or low water is. In practical terms, it is important to know within 30 minutes and 10cm what is going on. The unit's real strength is its ability to offer hourly height predictions at the press of a button, and we found this very useful indeed. It takes away all need for mental calculations and this can only be a safety factor - even if it is only used to check your own sums. The Tide-Mate is not a replacement for sound seamanship.