|Used on these elements|
|Tools for this tag|
To indicate a maritime administrative boundary, see boundary=maritime for more details on maritime boundary tagging. According to that maritime=yes is meant for tagging the 12 nautical miles territorial sea limit. Practically it is used for administrative boundaries that are located outside the coastline independent of their function and admin_level=*.
For water areas
To indicate a water area (tagged waterway=riverbank or natural=water) belongs to the maritime domain, i.e. it is connected to the ocean and ocean currents regularly lead to water transport in both directions. The meaning here is similar to tidal=yes but applies also in areas with little or no tides.