If you want quick basic information on all ports
, the first idea in my mind is to combine a simple wiki with a map. If it is simple and works well, people might start updating and using that information.
The wiki would have a simple template for all typical information of the port / anchorage. It could include links to other sources of information. A small local map with depths, piers and other facilities could be added. Dates (latest check / update) would be used to indicate the freshness of information.
The map would be just a simple clickable map (Google maps based or similar) that would contain links to the wiki pages.
If you want the app to work
also offline, some more work would be needed to store and display the maps and wiki.
Out of the given example sites zuluwaterways was closest to what I had in mind (simple, links in the map).
My point is that if it is simple enough, and would allow easy (wiki style) updates, it could work.