Shark Island

The island looks like a shark and contains a secret cave surrounded by fire. To extinguish this fire you have to press four switches in a specific order. First switch is a floor switch at the "head" of the shark, then go down to the "bottom flipper" and whack the plunger with your Skull Hammer, the third one is on the "top flipper" and just needs to be slashed with your sword, the final switch is at the "tail" and needs to be pressed down with your Iron Boots. Once all these switches have been pressed, the fire will go away. In the cave, there are hordes of Bokoblins and Miniblins, as well as Moblins and Darknuts and two Wizzrobes and Mighty Darknuts. Take out all these enemies and you will receive 200 rupees in a chest.

Also, unacknowledged by the Cyclos article, this island and the Mother & Child Isles have been known to have raging cyclones.