Legend of zelda: ocarina of time, water temple?

in the water temple there is a room with a WHIRLPOOL in it in the water there is what appears to be the head and tail of a dragon inside the mouth of the head there is a switch that leads to a different chamber. my questions involves that same room, in said room there is a ledge far above the surface of the water with no target for the longshot in it and u cannot change the water level. said ledge is very important as it leads to the room with the key i need, my question is how do i get to that ledge?