Cleats, piles, depths, whether the pontoon floats, and the note about the wind that only a local knows. Draw your own and publish it, or take one and sail it offline.
“Practise Marina X before I go there” is the sentence that sells this app to a sailor who has never heard of it.
Harbours that begin in OpenStreetMap are a derivative database, so sharing them means sharing them under the ODbL. The commons is therefore open by law before it is open by choice — and the choice follows.
Every contributed harbour is published under the ODbL, the attribution travels inside the file, and a dump of the whole commons is downloadable by anyone. A harbour behind a paywall is one nobody improves.
Tell us which one you would draw first.