The ocean used to be a boundary between countries before the invention of the steam engine. Now, it is a place for recreational activities and most importantly a source of food. The ocean is a challenge to some of us who swims across the oceans and sails round the world. Some of us just like to travel across the ocean on a cruise to nowhere.
To others, the ocean is just a body of water to conduct experiments like nuclear tests in the waters, destroying everything in the area. In the future, man might be living underwater, no one knows.