Map symbols for flooded/drowned cities

[Henkmet]

What symbols do maps use for cities that have became swallowed by the sea. I don't mean a seasonal flood, but really submerged? I guess on regional/world maps you can't do much better than a general city 'dot' in a different colour but on a smaller scale map like a topographical 50k or so?

[Chashio]

You can use whatever symbol you want to fit the style map you're creating, and if its meaning isn't obvious (ie. the symbol is an illustrated depiction of a drowned settlement) then add a key/legend to the map to explain the meaning.

[Henkmet]

Thanks; I had thought there were some standard symbols but in a way this means more freedom for me.