It was about an all water world, where people were living under water.
They'd manage by catching air bubbles that would float slowly under water by catching them in contraptions they'd wear on their head.
If I remember correctly, the planet was created by some sort of portal from Earth, to dispose of extra seawater.
The people that live on this planet couldn't surface because it's too close to (a) sun, so they would die if they did.
A thing I also remember is the core of the planet was this 'being' that had mind controlling abilities.