Only about 29% of the Earth is above sea level, so perhaps it should be called 'Water' or 'Ocean'?
For most of human history, almost nothing was known about the deep oceans.
The science of the oceans - Oceanography - is still full of chances to discover new things.
The deeper you go, the darker it gets, and most of the deep ocean never sees any sunlight.
To get a sense of the excitement of oceanography..
These oceanographers give a hint of their work.