As per 2010 figures to the global GDP of $ 60 trillion, the oceans have added a hidden and unnoticed $ 70 trillion. http://en.wikipedia.org/wiki/World_economy,
Why oceans are key to the global economy (courtesy Reuters .. )If Oceans were not there, world climate would have gone topsy turvy .. The contribution of ocean currents and the resultant trade winds to trade and world climate is beyond any comprehension. The Pacific Ocean (28% of earth surface, avg depth of 4km and max of 11 km) by itself covering about 155m sq.km is the largest of all the five and is app equal in size to all landmass on earth and slightly less than all the other oceans put together (180m sq km) !!
It contains water equivalent to 155,000,000,000 sq.m x 4,000 m = 620,000,000,000,000 cu. m of H20, ie. app. 620 trillion cu.m of water !
Oceans help us in many ways, besides giving oxygen, controlling global climate and rain ( that hidden source of water which nourishes the water bodies of the earth and its flora and fauna annually), it offers sea food, trade opportunities (80% trade volume and 40% trade value), tourism, livelihood to people, supporting other species (almost 50%), storing CO2 reserves and the like...
Let us appreciate nature around us and not belittle its contributions to making our human existence so pleasant ..!