|place = sea|
|A part of an ocean.|
|Used on these elements|
|Tools for this tag|
A large body of marine water and part of an ocean: seas Wikipedia:Sea, gulfs Wikipedia:Gulf such as the Gulf of Mexico, bights Wikipedia:Bight and very large bays such as the Bay of Biscay and Bay of Bengal
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Mapping seas as areas
Originally most seas (including large bays and gulf, such as the Gulf of Mexico and the Bay of Bengal) were mapped as nodes in late 2008: there were about 110 at that time. In 2014 and 2015 about a dozen additional seas were mapped as multipolygon relations. In late 2018 and early 2019, a number of sea nodes were deleted and large multipolygons were created instead. This is controversial, because most seas do not have verifiable boundaries with the open ocean or other seas. Also, such large multipolygon relations can be very difficult to maintain; they must be edited whenever the coastline is split or merged or a new island is created, and thus can be easily broken. For these reasons mapping seas as areas with multipolygons is controversial.
Note that oceans are always mapped as nodes, and most bays are mapped as nodes (There are 47,000 bay nodes vs 7,000 bay ways and relations as of mid 2019).
The trend to map seas as multipolgyons is related to the increase in mapping bays and straits as multipolygons, which also became more common at the same time, most likely due to a [change in rendering] by the Openstreetmap-carto style sheet, the style used by the standard map layer on openstreetmap.org. However, note that seas are not rendered by that style as of mid-2019.