The First Tunnel
This playground features a series of watery tunnels. Taking the proper turns leads you to a Piece of Heart and the masked child; taking the wrong turns leads you back to the start. Put on the Zora Mask and drop into the water, then strike the crystal switch to open a distant gate.
After striking the crystal, hold 
+ 
to swim down the following tunnel at top speed. When you reach the fork, swim into the tunnel on the left (the one with the school of fish).
The left tunnel leads you to the gate that you opened by striking the crystal switch. There’s a catch, though: you’ll need to leap up from the water at top speed, making Zora Link jump up from the water and fly past the gate before it closes.
Jumping out of the water at top speed causes you to fly past the gate and land on a high ledge. Go through the nearby door to reach the next tunnel.
The Second Tunnel
The second tunnel begins much like the first. Smack an underwater crystal to open a remote gate, then swim at top speed with 
+ 
to reach it before it closes. When you reach the three-way junction, pick the tunnel on the right.
The right tunnel leads to the gate. Make another daring leap from the surface to fly past the gate before it closes, and then proceed through the door to reach the final tunnel.
The Third Tunnel
Strike the underwater crystal to open the third tunnel’s gate, then step on it! Swim hard with 
+ 
to reach three tunnels stacked up on top of each other. The top tunnel leads to the gate, but don’t go there just yet. Enter the middle tunnel instead.
Swim through the middle tunnel until you reach the end, then swim hard for the surface, and leap out from the water with the help of the updraft. You’ll land on a ledge with a Piece of Heart.
Piece of Heart #51
You got a Piece of Heart! Collect four Pieces of Heart to assemble a new Heart Container. Each new container you put together increases the amount of life energy you can have.
After claiming the Piece of Heart, drop into the water and swim beneath the ledge to return to the start. Make your way back through the first and second tunnels, and this time, take the top tunnel on your way to the masked child.
Reaching the third tunnel’s gate is tough, as you must make two daring leaps up from the water this time. Use the first updraft to fly up onto solid ground, then run forward and drop back into the water. Swim fast with 
+ 
down the short tunnel that follows, and use the next updraft to leap up and through the gate before it closes. You have just enough time to get past the gate, so don’t dally.
Once you’re past the third and final gate, go through the door to meet the masked child. Take off the Zora Mask, and give him three more masks to return to the grassy field. You’re running out of masks by now!
One Last Game
If you followed this walkthrough faithfully and found every mask along the way, then you have just enough left to play the last child’s game. Save your progress, and then speak to the frolicking child who wears Twinmold’s Mask (the only child left besides the lonely one near the save statue). Give him four masks to visit the final playground.