How do you freeze water? I got through to this area after getting the "blue" stone, where you fight this blue knight thing, and that requires you to get over a small water pond. I know you need to change bombs to the type that freeze water but i can't figure out how to do that. I'm using a ROM emulator on a PC and use a keyboard.

I found A and Z make bombs go off, x lays them down and kicks them, c lets you pick them up and throw them. But nothing else seems to get it to change to these freeze bombs. And I can't go any further until I can freeze this stupid small water pond just before the steps