@eteb3 Thanks for the reply.
The tag is documented here:

"https://wiki.openstreetmap.org/wiki/Key:natural?uselang=en#Water_related"

If you search for "Any body of water, from natural such as a lake or pond to artificial like moat or canal. Also see water=river" you will find the specific lie.
A nearby example that uses this tag is:

"https://www.openstreetmap.org/way/562557777#map=17/38.712785/-9.223783"

My idea was  simply to mention there is a body of water present here, but perhaps some other tagging fits better, here?
