Hi, the changeset comment is not really suitable for making a query of the mapping community.
It is meant to just describe what you have mapped in the changeset you are uploading to help when others want to see the history of mapped objects or a brief summary of what was done in a particular changeset.
The question about the mapping of the bay would reach the right audience if you asked on the Oceania Community page at https://community.openstreetmap.org/c/communities/oceania/73 
I think the user login is the same one you use when editing.
Coastlines are mapped to the mean high water line so on a satellite image would often appear near the high tide debris line. If this is not a suitable reason for the problem you see please ask on the community page.