To learn more about the purpose and methods for researching U.S. legislative history, consult this report from the Congressional Research Service, Legislative History Research: A Guide to Resources for Congressional Staff.
You may also want to find this information for maritime treaties. Materials for treaties that typically include records of negotiations, discussions, and drafts are called travaux préparatoires. For a full discussion on finding these materials, see the Public International Law Guide - Treaties section. It includes a discussion on finding working documents and implementing legislation. As with the text of treaties, this discussion applies to all areas of the law (not just public international). A few examples of helpful resources are listed below, including some electronic and print materials.