The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From u-app UG (haftungsbeschraenkt):
Diving guide and travel companion to three very different Caribbean destinations: Its yo-ho-ho and a bottle of rum as this app takes you on a journey both above and below water through three of the Caribbeans finest destinations: Dominica, St Lucia and St Vincent. Its not by chance that the producers of the Pirates of the Caribbean movies chose these destinations as filming locations, yet the real treasures here are to be found beneath the waves. This application is a companion aimed at scuba divers but will also be of use to those that prefer to stay on dry land. It provides important information on dive centers, dive sites, weather conditions, as well as all the local information you need to ensure you make the right choices. The application is also beautifully adorned with images from a world-class underwater photographer. Before you invest in your trip, make sure you get this app!