The use of seawater and the exploitation of marine resources may cause serious damages unless they are carried out in a way that guarantees its sustainable use, i.e. that guarantees compatibility between the marine ecosystems and man’s activities. Unfortunately, in many cases, since the antiquity the sea has been wrongly considered as a huge dumping ground in which all waste and dirt could be freely thrown. And it is still considered as such by poorly educated summer tourists, especially those who use sailing or motorboats and throw all their waste into it. Today, the main causes of pollution in the seas and oceans can be:
pollutants from human activities discharged into the rivers and carried to the sea (degradable and non-degradable organic materials from urban waste, organic products of agricultural origin, such as plant chemicals and fertilisers, pollutants from industrial waste);
oil spilled by oil tankers, following accidents or improper practices when cleaning tanks or discharging ballast water;
radioactive substances: released during nuclear tests, by now stopped in all countries, and when producing atomic fuels;
overheating of coastal waters, due to hot water coming from industrial cooling plants;
excessive exploitation of fishing resources (too much fishing), that causes the fishing populations to decrease or even disappear;
uncontrolled urban development along the coasts and uncontrolled and massive seaside tourism;
discharge of nuclear and toxic waste;
discharge of plastic containers and other non-biodegradable solid waste.