Except this article is about irrigating with sea water to mix with fresh water. A salt water marsh is not a particularly concentrated salt water, and is diluted

Except this article is about irrigating with sea water to mix with fresh water. A salt water marsh is not a particularly concentrated salt water, and is diluted by rain and water flow above and under ground. The brine from desalination is extremely concentrated and toxic. In theory you could dilute it with large amount of fresh water to make salt marshes, but the entire point is to make fresh water from salt water. For a salt marsh you’re better doing as in the article you linked and pumping sea water from the ocean.