according to claudio:
da ghiaccio ad acqua: describes the change of state of water: from solid ice to liquid water.
dal ghiaccio all' acqua: describes something or someone (like a bear) moving from the ice into the water.
I hadn't been told about 'ad', but as I go over and over the same questions each day, to try and remember them, I knew about it because I'd been practising so much. It's the only way I can try to remember things without someone to physically ask.