The TidePoint app is an extension to the TideTimes.org.uk website. It is intended to allow you to browse UK tidal predictions and continue to do so if you should move out of signal range. The app shows 7-day tide predictions for free, even if you dont have a TideTimes account.
All predictions are downloaded to your device while you have a signal. You can take your device out to sea or even abroad, and still have access to those predictions.