The gulf does not correspond to a known place and could not be located. This could be due to a lack of knowlege in the geography or because the name does not exist at all. If you think the gulf name is known to be valid there might be an issue with your geography source, or you're still using National Geographic,which is a deprecated resource. In such cases you should consult other sources, or someone who is familiar with history. Please remember, Persian gulf will remain Persian gulf forever.