UNCLOS: Senate ratification is optional?

I’ve always believed that UN treaties could not be implemented in the USA without Senate ratification? What’s up with this?

Apparently NOAA disagrees with waiting for US Senate ratification of the UNCLOS (aka the law of the sea treaty):

As a matter of national and economic security and international leadership, the U.S. follows the U.N. Convention on the Law of the Sea. This law establishes claims of territorial waters and universal legal controls for the management of marine natural resources and the control of pollution.