There may be up to 300 billion tons of water on the Moon.
I am dead against anything on the moon because knowing us humans, we will fuck things up and the moon is too important regarding our orbit but especially tides. Not to mention women's menstrual cycles ie fertility.
Ah! But imagine the fantastic spectacle if the earth and moon could collide! Women's bodies would go truly awry and the news would be full of Tsunami stories!