Big Octorok

The Big Octorok is the boss of the Temple of Droplets and guardian of the Water Element.

The Big Octorok sits frozen inside a large room of the Temple of Droplets, along with the Water Element. It's not until the player can thaw the Big Octorok that you may fight him. Link finds switches around the dungeon that cause sunlight to pour onto the Big Octorok. When enough rays of sunlight are shone on the Octorok, the heat thaws both The Octorok and the Water Element, which the Octorok quickly gobbles up. He then retreats into a new room. Upon entering the Big Octorok's chamber, he starts spitting rocks out of his snout. Deflecting three rocks at the Octorok with your shield will damage him. After a number of hits, the Big Octorok will freeze. Using the Pegasus Boots and Flame Lantern together, run around to the Octorok's flower "tail" and set it on fire. Repeat the process three times.

The reward for defeating the Big Octorok is a Heart Container and the Water Element.

Somewhat interestingly, this is one of only two bosses in the Zelda series to be defeatable without the use of the sword. The other one being Twilight Princess' Blizzeta, which is also the boss of that game's ice-themed dungeon.

Quote from The Legend of Zelda: The Minish Cap Octorok figurine: "Appears in the Temple of Droplets. Frozen solid by the power of the Water Element. He's been frozen so long that his hunger is unbearable."