Let the current encourage you toward the right. Pass through spiked rings and use air blasts to take out any enemies and a bomb block, which reveals a doorway you should enter along the far right edge of the corridor.
In the next chamber, descend the waterfall and ride the 3D Warpstar you find at the bottom, which takes you to the start of a ledge just to the right. Head forward, taking out enemies to reach another of the 3D Warpstars. This one takes you to another waterfall and another 3D Warpstar, and then you're descending once more. Quickly head right and out of the water current so you're not swept into a spiked orb. You can swim back in and collect a Keystone, then continue descending along waterfalls in the same manner. When you reach one with an oversized fish, swim past it for the next 3D Warpstar, but then you need to get out of the water. It leads to another 3D Warpstar, but you want to swing wide and descend past the star to find a hidden door. Enter it.
Through that door, you'll find a short passage with enemies. Defeat them and grab a Sun Stone from the far right side, then return left and go back through the door. Now you're ready to ascend and ride the 3D Warpstar you previously avoided, which carries you to an underwater area with a huge eel that emerges from the right side of the passage. Avoid him and swim down to pass through another doorway.
Here, you will be tossed an Assist Star as the current carries you right, and there are capsules with the Ninja and Spear abilities. Take the one you prefer and continue right to a mini-boss battle.
Mini-Boss: Grand Wheelie
You have battled this guy previously. He is easy to take care of with a rush of Spear attacks, and the only real complication is an enemy at the middle of the area that fires shots upward to inflict small damage. You are better off sticking to one side (usually the right side, since you can move in quickly and take away half of your foe's life meter almost before the battle begins) and simply dodging a few attacks while you wail on your adversary. If you lose the ability, you can usually get it right back, and possibly even inhale and exhale a star to quickly do more damage. It's a short fight, if you do it right.
Once Grand Wheelie falls, you can quickly gulp him down for the Wheel ability. Then float right to find treats and a doorway to enter.
That door leads to a long passageway with another enemy that you can inhale for the Wheel ability, if you missed your chance just a moment ago. You want to quickly ride along the water, keeping to the low ledges. There's going to be an opening you can quickly roll through that leads along a low passage and to a
Sun Stone far to the right. You can then destroy a bomb block to reveal a narrow shaft overhead. Float up it and then pass through the door you find at the top.
In the next corridor, you're going to have to swim around the room's exterior in a clockwise pattern, as directed by current. You can swim right, down, left past an eel and then up to reach a 3D Warpstar, not far below where you entered. Then you'll have to make a similar circuit in the background, except counter-clockwise. As you start right, swim to the top of the passage and hit a bomb block with expelled air to open a passage. Swim up that passage to reach the stage's third
Sun Stone. Then head back down and continue right and up. There's a
Keychain here as you are pushed upward. Then as the current heads back left, let it carry you past the goal door. Swim toward the top of the passage and in that direction, you should barely see part of a black opening. Swim to it and press Up to enter a hidden chamber.
You're now being pushed down a waterfall. Let it carry you down toward the base to a 3D Warpstar. It will take you to another waterfall that inexplicably pushes you upward. Here, you need to weave between more 3D Warpstars (several of them) to reach the top of the area and collect the
Rare Keychain: Dimension Mirror. Then you can go ahead and return to the previous chamber and pass through the goal door to complete the stage.
NEXT: Wild World - Stage 3