What is the basis of judge-made maritime law in the United States? 

Judges in traditional maritime cases are charged to find and apply the “general maritime law” in their cases. The general maritime law is the epitome of a federal common law, based on precedents from other maritime courts and authoritative statements of law such as the restatements of law developed by the American Law Institute. Judges may also look to the way in which similar matters are handled in the maritime courts of other nations, to the historical treatment of such issues in the ancient or medieval sea codes, and to the corresponding state’s laws or related statutes.