Initially, when Link enters the room it appears to be empty. However, the Slime Eel's voice is heard, where it laughs and says he will eat Link. The eel's tail then bursts up through the floor in the center of the room and he bites two holes in the northern wall and southern wall. Its tail then starts moving in a circle to try and hit Link. He can jump over it using Roc's Feather or simply avoid it. The eel's head occasionally peeks out from one of the four holes. When the Nightmare's mouth opens, Link must use the Hookshot on it to pull the eel's body out of the hole and in to the open, where its weak point is marked by a flashing heart symbol. Link can hit the symbol with his sword.
After repeating this a few times, the Slime Eel is defeated. His final words taunt Link for not knowing about the truth of the island. At last, a Heart Container appears and Link can enter the next room, where the Wind Marimba is located.