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<pre>>><i> It is a bay of the Tasman Sea/Pacific Ocean. Ecologically it is a fully
</i>> maritime waterbody.
>
> What do you mean by "maritime waterbody"?
A maritime waterbody are all those waters under the influence of the tides. You can review article for natural=coastline. The coastline should be placed in the "high water mean spring": <a class="moz-txt-link-freetext" href="https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline">https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcoastline</a>
> If you're in Botany Bay or the other bays there such as
<a href="https://www.openstreetmap.org/relation/1333569,">> https://www.openstreetmap.org/relation/1333569,</a> you're not at sea or
> in the sea, or in the ocean.
Botany Bay is part of the ocean, not a separate inland waterbody. You can see in the terrain the mark of the tides.
> If you swim at a coastal beach you're swimming in the sea and the
> ocean. At the beaches of Botany Bay, no one would say you're in the
> sea or ocean. Nor would they say you're on the coast of Australia.
This is only a colloquial thing. That lacks of verifiability. For example, Dead Sea is not a sea, really is a lake.
> Botany Bay is unlike many conventional bays which are on the coastline
> and part of the sea. You're right that these types of bays are part of
> the sea and ocean, and other times they are part of a river, but
> botany bay is really a river nor sea, if anything Botany Bay sounds
> much more like an Esturary. <a href="https://en.wikipedia.org/wiki/Estuary">https://en.wikipedia.org/wiki/Estuary</a>
The rules for tagging are in the OSM wiki. Even in Wikipedia says Botany Bay is an oceanic bay: <a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Botany_Bay">https://en.wikipedia.org/wiki/Botany_Bay</a>
The coastline is a natural feature. You don't mix it with political things. You can use the tag boundary=maritime + maritime=base_line to delineate political inner waters. Even the boundary runs in the mouth of Botany Bay, therefore is respected local things that you mean.
Here there are instructions to tag an estuary: <a class="moz-txt-link-freetext" href="https://wiki.openstreetmap.org/wiki/Proposed_Features/Coastline-River_transit_placement">https://wiki.openstreetmap.org/wiki/Proposed_Features/Coastline-River_transit_placement</a>
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