Should there be a comma between adjectives 'ghostly' and 'sunken' in the sentence below? Is sunken even an adjective here?

Apologies – I know that there are many posts around comma usage in coordinate and cumulative adjectives but I seem to have a mental block with this sentence:

They swam around the ghostly, sunken ship.
They swam around the ghostly sunken ship.

Is the comma correct? It could be a ghostly and sunken ship in which case the comma would be correct, I think. Or is sunken ship considered as one so ghostly is the only adjective? In which case, it would then be without a comma.

Which is correct or does it not really matter?

Thanks