What are the main international treaties addressing the problem of water contamination?

The Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (London Convention) was held in 1972 and sought to establish laws and protocols to address the issue of ocean pollution. The Convention led to the establishment of the London Protocol in 1996, which prohibits the dumping of wastes from sea vessels, aircraft, and other man-made structures into the sea. The London Protocol also prohibits the dumping of the vessels at sea. Participating countries are expected to issue permits for disposing wastes at sea. Additionally, dumping of some wastes considered hazardous is completely banned by the protocol.
The International Maritime Organization has also established treaties to address the issue of ocean and sea pollution. The International Convention for the Prevention of Pollution from Ships of 1973 sought to prevent and address accidental and operational pollution by ships at sea. The Protocol following the convention was adopted in 1978. The instruments cover the prevention of oil pollution by sea/ ocean vessels and the discharge of waste and effluent by the vessels.
https://www.epa.gov/ocean-dumping/ocean-dumping-international-treaties