In December 1970, the United Nations General Assembly (UNGA) adopted two resolutions of major significance for ocean and freshwater resources. One of them, Resolution 2570 (C) (XXV), related to law of the sea, the seabed, and the ocean floor; and the other, Resolution 2669 (XXV), related to international watercourses. The resolutions set in motion two parallel, lengthy, and complex processes that resulted in the adoption, at different later stages, of two conventions, namely the Convention on the Law of the Sea in 1982 and the Convention on the Law of the Non-Navigational Uses of International Watercourses in 1997. This article discusses and analyses the international environmental law aspects related to ocean resources as well as those related to freshwater resources. It considers marine resources and the conservation of the marine environment, marine pollution, regulation of vessel-source pollution and ocean dumping, the principle of equitable utilisation and the no harm rule, and multilateral and bilateral agreements.