Why saving our oceans is the most important problem for the world to solve

First to say we have a lot of problems to be solved beside the oceans but the fact that a huge part of our earth is covered by the sea (about 70%) means that changing in this ecosystem will have a huge impact on all the rest of us! It doesn't matter if it is the garbage and waste that toxicate our seas or the amount of fish that will decline even further by too much fishing. All life started by the sea and we all depend und this system. If temperature changes by melting the pole we all will notice the impact. And without an awarness for this important part on our earth all other efforts will be useless, because without the see there will be no rainforest, nature or even human!