If hes in a bubble, but not above the water, he would be underwater. Meaning he would float to stand above his bubble if there's enough water there, bringing the bubble with him keeping him underwater. So, he would shoot strait up like a rocket, or perhaps liftoff before the rain touches the ground...

Is there an upper range on the power? What if a waterworld a billion light years away is directly overhead? Dose he travel to a surface faster than his human form could survive?