The ocean covers over 70% of our planet.
And yet, what we know about it barely scratches the surface.
Beneath its swell is a largely unexplored universe, until recently, beyond the gaze of human eyes.
So why do we know so little about the ocean?
For a start, immense pressure presents huge challenges for divers and equipment alike.
In many ways, it's easier to send a mission to space.
But with new technology, such as submarine robots, this hidden realm is starting to reveal its secrets.
So, what's down there?
Well, there's water. Lots of it.
1, 419, 120, 000 cubic kilometres, to be about as precise as you can be.
