Please note that the tag "natural=coastline" should not be attached to nodes, only to ways

I have added an OSM note for someone to check access. As I said in my original chnageset comment, this path exists on the councils ROW dept dataset, released last summer

I'm pretty sure it was changes before mine which broke the relation. When I fixed overlapping coastline issues in this area I maintained relation members on the ways I directly edited.

I am not personally disagreeing with your mapping style. It is a long standing OSM convention that the coastline tag is not used on small water bodies not connected to the ocean.

As far as I am aware the only exception to this is the Caspian sea, which due to its size would be impractical to use a mulitipolygon tagged as natural = water.

Could you please explain what you mean by a "permeable embankment"

Just to be clear a body of water which is not connected to the ocean should not be tagged with coastline. Either this body of water is tidal, in which case it cant be a closed body not forming a continuous interlinked coastline with other coastine ways, or is is not tidal and it is should be tagged as natural = water.

I note that you have once again incorrectly used the coastline tag on the ways south of the embankment. I have now fixed this in changeset/135422329

The ways to the south of the embankment were tagged as coastline by the user harahu_import. If you have an issue with that tagging I suggest you take it up with that user.

I didnt come up the the boundary. the wats in this relatiuon were drawn by user droki in changeset changeset/72452429 . However he had mis tagged the role of one of the inner ways, and my changeset (the one you are commenting on) fixede that error

I have corrected the spelling, the reason i chose atoll rather than reef, is that the way I tagged is the inner way of a realtion which is the reef