ocarina of power level4 help

Great game!...I'm stuck! I have completd levels 1-3...got candle,
bow and arrow, boomrang, ocarina, and hookshot. Should I also have the hammer? Got first key in level 4...but can't find second one. I walked through the wall going right to find a room with a stairway, but separated from it by water....can't use hookshot blocks are inway of using it. What am I doing wrong?
thanks in advance for any assistance. Hurry...I'm going nuts not being able to continue...:cry:

Nevermind...already answered!