You will furthermore discover two nice spoilers: A.) I am planning to display the official warning levels for each gauge station. B.) at least for the german stations (thanks to german bureaucracy) I already have historical river levels. My plan is to visualize them with a boxplot - so you'll even know if the actual level ist usual for this season or already unusual high / low.
Furthermore you can compare some technical data across all ships http://www.rivercruiseinfo.com/content/compare-ships . I gathered theses data from all different kind of sources, boards, ship spotting sites, investment group pages and so on. Therefore they are officially unproven but quite accurate. Especially interesting might be the minimum and maximum draft of ships.
For the next feature I need your help. I would like to include pictures of cities & ships. Not the fancy high resolution professional stuff used in advertisement (though I certainly would not mind a certain quality), but the real stuff - how these ships (their equipment & cabins) and cities really look like. Status so far: I got ca. 15 / 400 cities myself and ca. 40 - 50 / 250 ship photos (outside only). Therefore I am really looking forward for your help, as you have been out there on the cruises