On September 25, 2015, UN General Assembly adopted the 2030 Agenda for Sustainable Development: it is a plan of action for people, planet and prosperity articulated in 17 Sustainable Development Goals. 

Two of them are of primary importance:

Goal 13. Take urgent action to combat climate change and its impacts;

Goal 14. Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

Actually, these two goals should be in the first two places, because climate change and its consequences affect all men on the planet, rich and poor, and because knowledge and protection of marine environments are fundamental to the global balance of resources.

Seas and Oceans cover 71% of the Planets surface: not surprisingly, there are those who claim that our Planet should be called Ocean and not Earth. The Oceans are not only the cradle of all the life we know: it started there and then conquered the lands. 

The Oceans are the engine of the global climate and their conditions will determine the evolution of the future life of all the organisms that populate the planet, including human beings.

We know very little of the Oceans and not only about their deepest recesses: even the shallowest coastal areas of a large part of the planet are unknown. Thus, also marine life and its changes are largely unknown. This ignorance becomes even heavier in the face of the speed of change induced by the rapid evolution of the climate forced by human activities.

Knowing the sea is difficult. On earth we are able to reach every corner of the planet directly, to know every nuance of its surface and of the organisms that populate it through direct exploration, increasingly thanks to the tools of technology. The resolution of satellite images, the capacity of specialized sensors to describe more and more sophisticated parameters has taken away much of the mystery of “what’s behind the hill”. Yet new forms of life continue to be discovered.

The sea is opaque to instruments and sight: the satellites read its surface, but are unable to read except at very shallow depth. Electromagnetic waves stop at the surface and satellite geolocation (GPS or other systems), which is normal on land, under the sea does not work. 

On the mainland the visible horizon is miles away from the observer and if there are no obstacles it reaches the limit of the earth curvature. 

Therefore if observing the sea while standing on the shore the visible horizon is about 5 km; in the submerged environments the visibility rarely exceeds 40 m and in most cases much less. Under the sea the other side of the hill is not miles away, but a few meters from the observer.