You have almost crossed the huge sea of Ripple Field, but another obstacle lies ahead. An enormous whirlpool stands right in your path, and you have no choice but to dive in. You will need Kine to navigate yourself in these treacherous waters, but another one of your Animal Friends' relative lives here. If you want the Heart Star, you're going to have to find that friend of yours within this whirlpool and bring him safely to his family member.
Into the whirlpool
At the start, simply drop into the water and have the strong currents drag you to the bottom. Go through the door there to reach an underwater section with even more currents. Again, let the currents carry you to your destination, but this time, you must also actively avoid the Glunks and Joe in this section. If you can, try to get the stars littered around here, as you can collect about half an extra life from the amount of stars here. Going through the door at the end, you will end up in a small chamber with Kine. You must get Kine to progress, as the following section contains a strong current that must be overcome with Kine's swimming capabilities.
Once you get past the current with Kine, you will resurface into a section with more dry land. There are some Sparkies here if you want the Spark ability, while Squishies and Babuts also populate this area. When the path first splits, go down the lower path to reach a door leading to a small room with a Galbo and some stars. The Galbo is a simple enemy that spits fire when you get close to it, and it also grants you the Burning ability. You definitely want to get the Burning ability, as it is part of the method required to get the level's Heart Star.
Return to the main area and continue onward. The path will soon split again, with the lower path blocked by a multi-layered wall that requires the Burning and the Stone ability to break through. The upper path contains a very small passage that cannot be crossed by Kine, forcing you to continue alone. However, there is a Rocky slightly further into the level that will give you the Stone ability, which you can use to break the wall in the lower path, letting you get Kine across. As you need Kine for this level's Heart Star, you will certainly need to do so if you wish to collect it. Continue down the winding path to reach the door, with a Maxim Tomato hanging above it if you need more health.
Heart Star: Pitch visits his mother
This next section consists of several cycles of water currents spinning around in one direction, with small passages connecting each. With Kine, it is much easier to navigate this area. If you want to get the Heart Star, swim against the current down the left passage of the second current circle to reach a door. Inside is Pitch, who you must partner with and take to the end of the level to get the Heart Star. Back in the main area past that rotating water current is an Invincibility Candy, which helps you avoid taking damage while being thrust around by the currents. If you still have Kine, one of the rotating currents will have a Maxim Tomato and a 1-Up of to the side that you can collect if you swim against the water current. Eventually, you will reach the door to the next area.
Out of the deep sea
As you rise back to the surface, you must confront alternating water currents, each that will push you toward a Gordo on one of the sides. The key to getting to the door unscathed is by staying in the middle. The further you get from one Gordo, the more dangerously close you are to the next, so stay around the middle of the path and keep moving upward to avoid taking damage. Through the door, the murky green seas are a clear blue once more. Swim up and jump across the platforms to get an Invincibility Candy. Rush through the remainder of the level while invincible. Keep going right, carefully attacking the enemies in your path, until you reach the exit door. If you have Pitch with you, you will meet his mother Hiiru at the end of the level, who will grant you the Heart Star for bringing Pitch to her!