[NTJedi]

There was a major gameplay change where water mages could no longer enter water provinces in DOM_3. This hurt the SP games as the AI which previously had some difficulty entering the water now has extreme difficulty entering the water. In answering your question... the description was never updated.

As a result if you're playing SP games with no water nations... you want to have very little or zero water provinces otherwise it provides the human player an unfair advantage.