At this point Link has to know that he is getting closer than ever to recovering the Water Medallion. All that's left is for him to find the Boss Key and confront the watery demon that greedily guards the only item that can deliver salvation to the Zoras.
Get Pushy
Ensure that the water is still at its maximum height, and enter the third floor passageway that's to the right of the main entrance. Strap on the Iron Boots and drag the huge block that's found in the tunnels.
Tektite Nest
Once again, Link should wear his Iron Boots and sink to the bottom of the half full chamber. A tunnel on the bottom floor leads to a room where Link must use his Longshot to avoid a wall of spikes.
Underwater Switch
Link's next challenge is a room with an underwater switch. The place is crawling with Stingers, so these swarming enemies should destroyed immediately. Link can bomb the wall in two places, which reveals a hidden block.
Boss Key
Link will find another crystal switch, which causes three geysers to simultaneously erupt. Link can use the geysers as platforms to safely cross the gap.
End of the Road
The water must be raised to its highest level one last time, then Link will finally be able to use his Longshot to reach the ledge that holds the statue and the final door. Link can stock up on Fairies by smashing the jars that are found on this ledge.