Arrghus

Arrghus was a large Jellyfish who made it's home in the WaterGate Dungeon in Link to the Past. The Invertebrate was covered in several minature polyps which are known as arrgi. The Player had to rid Arrghus of these arrgi in order to expose it's body, to do so, one must use the hookshot to pull the babies away and then they must use their sword to slash them until they disappear. When all the Arrgi are destroyed, Arrghus bounces around the room as a last resort to kill Link, at this stage, it just needed to be slashed with the sword several times.

Link claimed the second crystal and a heart container as a reward for slaying the giant beast.