Walkthrough
Lake Hylia has been drained, and the Lakeside Laboratory is under suspicion — the scientist inside lets you through once you show him you’re carrying the Master Sword. The route to the temple runs through the Ice Cavern near Zora’s Fountain (frozen over by King Zora himself, trapped in red ice): inside you get the Iron Boots, needed to sink and walk along the floor of the Water Temple.
Back at Lake Hylia, Sheik teaches you the Serenade of Water. The whole temple revolves around a central mechanism that raises and lowers the water level — switching levels with the Iron Boots on or off is the core mechanic of the entire dungeon. The Longshot comes from defeating Dark Link, an optional but highly recommended fight in a mirrored room.
💡 Mentally note which water level you need before you swim to a door — changing height while already underwater is much slower.
Boss — Morpha
Hookshot (or Longshot) its floating nucleus to reel it in and slash it with your sword. If it catches you, it drags you inside its water body — move fast with the stick to break free before you lose too much health.
Defeating it wakes Princess Ruto as the Sage of Water.