MPPA chairman Ranjith Kularatne said most people were not aware that 90 percent of the pollution of the island's waters came from activity on land.
These include pollutants from agriculture and industry like pesticides and effluent as well as household waste.
Pollution from sources at sea came from shipping accidents, disposal of ship borne waste and oil exploration activities.
Pollution of the sea from land is increasing because of urbanisation and migration of people and industry towards the coastal belt, Kularatne said.
"If left unchecked, pollution could cause irreparable harm to marine resources like fisheries, as well as tourist attractions like coral reefs," he said.
Population pressure was a key cause of increased pollution from land with migration of people and industry towards the coastal belt and increased urbanisation in towns like the capital Colombo and southern Galle.
About 65 percent of the organised industry is on the coastal belt.
Effects of ocean pol