A wet or moist region with water standing on or just below the surface of the ground, and usually covered by a growth of vegetation

Data Dictionary for swamp_poly: http://apps.linz.govt.nz/topo-data-dictionary/index.aspx?page=class-swamp_poly

This layer is a component of the Topo50 map series. The Topo50 map series provides topographic mapping for the New Zealand mainland, Chatham and New Zealand's offshore islands, at 1:50,000 scale and replaces the NZMS260 series.

Further information on Topo50: http://www.linz.govt.nz/topography/topo-maps/topo50