It's the flooding problem most of all. I'm in one of the few Manhattan co-ops that still allows washing machines and dryers and it's a wonderful thing to have it in my apartment. But many landlords, co-op board and condos don't permit them because of the flooding.
Sodium acetate or hot ice is an amazing chemical you can prepare yourself from baking soda and vinegar. You can cool a solution of sodium acetate below its melting point and then cause the liquid to crystallize. The crystallization is an exothermic process, so the resulting ice is hot. Solidification occurs so quickly you can form sculptures as you pour the hot ice.
Answer 3: Dry ice is called dry ice because the solid turns to gas when heated, without turning into a liquid first. However, if we apply pressure and heat, we can turn it into a liquid, and sure, we can swim in it. We know this because of something called the phase diagram of carbon dioxide (the stuff of dry ice).