All coastline should be connected. I did quick check and looks like 461982097 also not connected.

Coastlines in OSM is how we define ocean-land border. Rivers are drawn in other way. Probably, there are some exceptions.

Unfortunately, revert is not complete. There are still a lot of mess like way id=97503875

This is a river and coastlines shouldn't be here. Please, read carefully about OSM coastlines and use JOSM to draw and validate them.

You added new coastlines that are not connected. This is a river bank here and I suppose these coastlines should be deleted. Please, use JOSM Validator.

Around way id=362901761

Coastlines are broken.

Coastlines are broken. Please, review.

Is it really necessary to draw separate sidewalks along the roads? Especially in BA (as far as I can see) all highways have a separate sidewalk, so maybe adding sidewalk:both=separate is enough here?

Well, may it has problems, but this way is definitely not a coastline.

And, please, a built-in validator for coastlines in JOSM.

If you reconsidered coastlines in this area, should remove natural=coastline tag from:
way/1184968553
way/1046894948

Otherwise, coastlines are not connected - broken.

I strongly recommend you use JOSM when editing coastlines. It has different validators to automatically check for errors.

Coastlines are very sensitive data and they should be correctly ordered and connected. Without ambiguities.

Coastlines are broken.
Decide which one of yours drawn to take: ways 1185155573 or 1185370240

In this case, "access=no" also looks ok :)
Not sure how to make it better, but "motor_vehicle=yes" should be removed in any case.

Hm, or even like this:
- hgv=designated
- bus=yes
- vehicle=no
To forbid all other vehicles like motorcar, motorcycle, bicycle, carriage, ...

If Paseo del Bajo is exclusively for trucks and buses, you should:
- remove generic "access=no" tag
- remove generic "motor_vehicle=yes" tag
- add specific "motorcar=no" tag

So the result access tags will be:
- hgv=designated
- bus=yes
- motorcar=no

OMG, coastlines are broken, JOSM shows > 2000 errors with duplicates ..

No problem. Use JOSM and don't forget to run Validator after your changes. Good luck with your mapping :)

Coastlines are broken after this change.

I understand, my point was that now the routing engine can't distinguish car shuttle stop vs bicycle/pedestrian stop.