14 U.S.C. § 2744: Life-saving medals

if such rescue or attempted rescue is made at the risk of one’s own life and evidences extreme and heroic daring, the medal shall be of gold; if such rescue or attempted rescue is not sufficiently distinguished to deserve the medal of gold, but evidences the exercise of such signal exertion as to merit recognition, the medal shall be of silver. In order for an individual to be eligible for the Life-saving Medals the rescue or attempted rescue must take place in waters within the United States or subject to the jurisdiction thereof, or if the rescue or attempted rescue takes place outside such waters, one or the other of the parties must be a citizen of the United States or from a vessel or aircraft owned or operated by citizens of the United States. No individual shall receive more than one gold medal and one silver medal; but any individual who has received or may hereafter receive a gold or silver medal and who again performs an act which would entitle him to receive another medal of the same class may be awarded, in lieu of a second medal of the same class, a gold or silver bar, as the case may be, to be worn with the medal already bestowed, and for every such additional act, an additional bar may be awarded. Medals and bars in lieu thereof, authorized by this subsection, may be awarded posthumously.