Oceans and seas represent an endless mystery. Their waters cover most of the planet and provide 99 percent of the inhabitable space for living beings – in other words, plants and animals – in a world that we, perhaps ironically, call 'Earth.'

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Oceans are usually associated with enormity, given their dimensions and the stunning biodiversity they hold in their saline waters. Nevertheless, they face grave threats. Their chief enemies are pollution and over-exploitation through activities that originate on land.

The relationship of our civilization with the oceans is marked by their unavoidable presence in our lives, the center of numerous human activities, and of many cultures, vocabularies and adventures. And now also because of the initiatives to defend the quality of the environment.

The planet, according to human geography, has three oceans and 18 seas, each with a regionally defined vocation. ''The sea unites nations instead of dividing them,'' affirms the executive director of the United Nations Environment Program (UNEP), Klaus Topfer, referring to the need to work together to prevent their degradation.

Those who want to navigate the oceans, but via the Internet, can embark on an adventure through the following websites, surfing the fascinating world of water and learning about the urgent need to prevent its destruction.