[[http://wiki.openstreetmap.org/wiki/OpenSeaMap/Seamark_Objects|Seamark Objects]]

{{{
osmosis --read-pbf file=netherlands.osm.pbf --way-key keyList=seamark --tag-filter \
seamark=anchorage,anchor_berth,berth,ferry_routem,lock_basin,navigation_line,platform,production_area,\
port_area,precautionary_area,recommended_route_centreline,recommended_track,restricted_area,seabed_area,\
sea_area,seaplane_landing_area,shoreline_construction,submarine_transit_lane,terminal,separation_boundary,\
separation_crossing,separation_lane,separation_line,separation_roundabout,separation_zone,turning_basin,\
two-way_route,vehicle_transfer,wreck reject-relations --used-node --write-xml seamark.osm
}}}

{{{
osmosis --read-xml file=extract.osm --tf accept-ways seamark:type=navigation_line,harbour,recommended_track,anchorage,restricted_area,berth --write-xml file=sea3.osm
}}}