Coastline and a large unknown line

This line is completely untagged, and seems to be some kind of outdated coastline. However, I would not delete it (yet), because:

• It may be some kind of work in progress (4 edits in the last 2 months)
• It may be part of the current coastline, maybe inadvertently damaged by one of the edits (look at the bottom part of the way, there is no coastline way except that)

You may try to edit the coastline, removing the old parts (like the one shown in your screenshot) together and keeping the parts for the areas where there is not other way defining the coastline.

You may also try to reach the other users involved in the last edits to know what is happening.

Keep in mind that coastlines, when edited, sometimes take several months to appear updated on the public tile server (this update is very expensive in computational terms).

EDIT: Looking more closely to the area, I would say that the way could be deleted safely - it matches (but with lower quality) the coastline and extends inward to where a lake already exists. Its first date is very old, maybe some old import or automated fix (see that it was uploaded by "upload.py"), by user "BugBuster" (see its wiki page). The changeset is also tagged saying something about splitting very long ways (more than 2k nodes, not allowed since a long time ago...)