The Water Temple is arguably the most infamous dungeon in all of The Legend of Zelda series. It was featured in The Legend of Zelda: Ocarina of Time and is known for its immense challenge - being considered by many as the most challenging dungeon in all of the franchise. Using the Zora's Tunic is a requirement in this dungeon, as many of the segments make Link go underwater for quite some time. The Iron Boots are needed to actually enter the stage, and using both of these items together will allow the player to walk on the bottom of the water for as long as you want. You'll be required to play Zelda's Lullaby throughout the stage on multiple occasions using the Ocarina.
Apparently, this temple, which is featured in Lake Hylia, is a tribute to Lord Jabu-Jabu. The Lakebead Temple featured in The Legend of Zelda: Twilight Princess, seemingly is placed in the same spot as the Water Temple, albeit the difficulty level has been considerably toned down.
Bosses and enemies
The ever popular Dark Link appears in this temple not as a boss, but rather as a mini boss. All of his attacks reflect the regular Link, though he also possesses even more abilities such as being able to vanish and reappear in different locations. The final boss of the dungeon is Morpha - a terrifying boss seemingly created by Ganondorf. It is capable of controlling every drop of water in the room it can be found in, proving to be a challenge for Link to defeat. Other enemies featured in this stage that aren't bosses are Blue Tektite, Shell Blade, Stinger, Spike, Like Like, and other, non-living traps.