If you own the Zora Costume, choose it.
Take control of the doppels and have them pick up a Gripshot on the left and right sides of the room. (You can also take one of these items.) Take control of an armed hero, shoot the Gripshot at the fence to the north to be pulled over to it, and go down to fall back. Do the same with the other Grishot-using hero. Next, switch to the unarmed hero, have him swim towards the hero on the left, lift him and throw him higher up. Switch to the left hero again, place him on the right edge of the platform (facing the orb) and shoot the Gripshot. Then quickly, take control of the hero on the right and do the same to make a platform rise at the centre of the room. Swim to this platform and shoot the Gripshot at the handle to the north so the wheel will turn and the water level go up again. The unarmed Link can now grasp the Water Rod! Have the other two heroes join him, make a three-Link totem with the Water Rod-using Link on top, and use the rod to create water pillars which will allow you to reach the north side. Place all three heroes on the Triforce gateway.
Have the heroes walk down on the large switch to make enemies appear. Place a Link with a Gripshot on the small platform to the north-east and the hero with the Water Rod on the north-west one (or vice versa) and use their items to attract and stun the foes that you then need to strike. When they are all defeated, the gate will open. Make a full totem, stand in front of the wheel to the north-east and shoot the Gripshot at the handle, which will make the water level go down. Next, swim towards north-west while passing under the fence. Make a totem with the two Gripshot-using heroes and place them facing the handle of the wheel but not on the grate. Next, take control of the other Link, place him behind them, use the rod to make them go up, quickly totem up with them, then fire the Gripshot at the wheel, which will make the water level go up again! Go back to dry land on the right and step on the Triforce symbol.
Take control of a Gripshot hero, use this item on the small square fence to make it flip, then go down to fall into the water on the other side^^ Stand on the switch nearby, then do the same with the other Gripshot-using hero and place him on the switch on the right. The gate will lower and disappear. Switch to the Link left behind, swim towards the centre of the room, then use the Water Rod towards left to reach an elevated platform. Bring the other two heroes on this platform at the centre, make a totem and throw a hero on the leftmost pillar (of the three). Switch to this Link, shoot the Gripshot at the hero to the left to catch him up, then fire the Gripshot at the wheel to make the water level go up. Bring back the Link located to the right, totem up with the other Gripshot hero and place them on the left, facing the square fence more to the north. Shoot the Gripshot to have a hero go through to the other side, then open the chest holding 20 rupees and jump on the raft. Fire the Gripshot at the peg to be pulled to the right, then have the other Gripshot-using Link join you. Make a totem, throw a hero towards the chest and open it to find a key! Next, step on the switch to lower the gate. Switch to the other Gripshot Link again and bring him to the hero with the rod. Make a totem and shoot the Gripshot at the wheel to make the water level go down. Next, climb back on the raft and have the Link with the key jump on it as well. Now use the Gripshot on the fence to the south, then on the different wooden poles to reach the locked door. Open the lock, then switch to the Water Rod hero, make totems to throw the heroes higher up and use the item again to catch them up. Stand on the Triforce to transport to stage 4.
Walk to the arena to face the second boss: Arrghus! Shoot the Gripshot at his red balls to pull them to you and strike them with the sword. For the ones located under the water, use the Water Rod to move, make them go out, then strike them. Next, the water will withdraw and the second phase will start. Make a two-Link totem with a Gripshot-using Link on top, wait for Arrghus to throw a red ball, then shoot the Gripshot at this ball to pull it and slash it. Repeat this technique with the other balls (which can take time). Next, the third phase will start, where Arrghus shows his eye and launches attacks with a great range. Make a three-Link totem and fire the Gripshot at his eye. As soon as he is hit (he's stunned), throw the top two heroes, run to the boss and strike him as much as you can. Next, stack all three Links again and repeat these tactics twice to beat him definitely! Stand on the Triforce symbol to go on. As usual, walk to the chests and choose one to get a new material. Level completed.
Back in the castle lobby, you can pay a visit to Madame Couture to see if you can buy a new outfit.