Since their publication in the 1950s and 1980s respectively, the Commentaries on the Geneva Conventions of 1949 and their Additional Protocols of 1977 have become a major reference for the application and interpretation of those treaties. The International Committee of the Red Cross, together with a team of renowned experts, is currently updating these Commentaries in order to document developments and provide up-to-date interpretations of the treaty texts. Following a brief overview of the methodology and process of the update as well as a historical background to the Second Geneva Convention, this article addresses the scope of applicability of the Convention, the type of vessels it protects (in particular hospital ships and coastal rescue craft), and its relationship with other sources of international humanitarian law and international law conferring protection to persons in distress at sea. It also outlines differences and commonalities between the First and the Second Conventions, including how these have been reflected in the updated Commentary on the Second Convention. Finally, the article highlights certain substantive obligations under the Convention and how the updated Commentary addresses some of the interpretive questions they raise.