re: That sinking feeling
Well, obviously I was referring to an environment with SOME gravity, otherwise "float in water" has no meaning.
But as the gravity changes, the weight (not mass) of a floating object and the weight of the water displaced changes in the same ratio, so that if a boat has a draft of 12 inches on Earth, it would still have a draft of 12 inches on a planet with twice the gravity, or half of it (assuming liquid water is available.)
Would apply to balloons, too, I suppose.