All in good time !
The newly created ocean's water will evaporate by the power of the sun, create clouds which will pour down sweet water which in turn will create rivers . . .
If one third of the earth is soon going to be submerged by melting pole ice . . . the cost of bringing the surplus water to the moon will be offset by the saving of agricultural land to feed the masses !
And who knows . . . eventually the earth will have a little sister out there !
One thing is sure . . . the surplus ocean water we bring there will not disappear into outer space . . . cuz the moon DOES have its own gravity !