Ideas for OSM & OpenSeaMap.
Leaving out the most detailed tags, the first question to be solved is how to tag port areas.
IHO definition of port: A place provided with terminal and transfer facilities for loading and discharging cargo or passengers, usually located in a harbour.
A first draft proposal could be
landuse=port port:facility=passenger_terminal, oil_terminal, cargo_wharf,.. port:category=container, RoRo,..
http://wiki.openstreetmap.org/wiki/OpenSeaMap/Harbours#Harbour_Categories and http://wiki.openstreetmap.org/wiki/Key:harbour:category should be used only on the total harbour if it's a specialized one (no other port types in the same harbour)
This excludes well established tags like waterway=dock or leisure=marina