Water, sea, oceans have invaluable ecological significance. The protection and preservation of the quality of water, sea and ocean are important not only for the flora and fauna, but also for the humans itself and for our economic and social development. On the other hand, oil is an important source of energy of industrial civilization and is irreplaceable for our society, simply daily human life would be unthinkable without oil and its derivatives. The transport of oil by sea occupies an important economic branch, which uses oil pipelines and specially equipped tankers to transport oil. Unfortunately, we are witnessing that, in addition to the transport of oil, tanker accidents are inevitable, which cause permanent risks for marine pollutions. An oil spill into the marine environment is an unwanted "catastrophe" with severe consequences that disrupts the survival of flora and fauna and consequently causes permanent damage to the marine ecosystem and thus to human himself. Any pollution of the marine environment with oil causes serious consequences for the flora and fauna of the sea as well as for people who lives near the polluted area, which affects their overall quality of life. This work includes an overview of the largest tanker accidents and their impact on the environment, which occurred during the last and the beginning of this century. The biggest tanker accidents are described and the consequences of which are still felt today. The Marpol Convention, an international convention that includes regulations for the prevention of pollution of the marine environment by ships from operational or accidental causes, which has been adopted and applied by the Republic of Croatia, has also been singled out.