The story opens to a calm and clear sunny day at the beach. Kirby, wearing his scuba mask and snorkel, jumps headfirst into the water. While swimming with some Blippers and passing a Glunk and a Squishy, Kirby sees a big pink pearl glowing nearby. Kirby swims towards the pearl and then out of curiosity, touches it. Suddenly, pink auras coming from the pearl envelop Kirby and then a flash of pink light occurs. As Kirby opens his eyes, he notices his arms have been turned into fins, his feet turned into flippers and has scales all over his body. Shocked by his appearance, he swims back to shore. But then he starts suffocating, unaware that he now has gills. Kirby's animal friends Kine and ChuChu, leap out of the water and drag Kirby back into the sea, saving his life.
Kine: Hi Kirby, can you understand me?
Kirby suddenly reacts to what Kine is saying.
Kine: I'll take that as a yes.
ChuChu: Don't be scared, it's us! We're your friends, remember?
Kine: It has been a while since our last adventure, but you don't remember us actually talking to you before. Look, this all will be explained later but right now we need your help. Come with us.
The two start swimming out to the sea with Kirby following after them. Once they had made their way down to the ocean floor, they spot an underwater Atlantis-like city under attack.
ChuChu: Oh no, it's happening again!
Kine: We better get down there quick!
Kirby looks worried but then starts to feel confident and they all swim towards the city. Once they've arrived, they see small, several yellow bipedal submarines with mechanical claws and blue eyes scavenging through the rubble, taking whatever loot they could find. Just then, they see the trio, so they drop everything and pull out harpoon guns at them.
Kine: What are you waiting for, Kirby?! Show them what you're made of!
Kirby takes them on. After defeating the last of them, a bunch of dolphins come out of hiding and start applauding at them.
Kine: This is more like it!
ChuChu: What are you talking about? They're clearly cheering for Kirby!
Two dolphins wearing armor and wielding spears approach the three.
ChuChu: The king and queen are expecting you, Kirby. Don't want to keep them waiting.
The three follow the dolphins to a jewel-encrusted palace. As they make their way to the throne room, they see both a male dolphin and female dolphin dressed in royal garb.
King: So this is the hero from the surface. Can't say that we're entirely impressed.
Kine: Trust me, this guy can do anything!
Queen: Well that does sound quite believable if I do say so myself!
King: Kirby, is it? I personally welcome you to our kingdom. We are the Dolphinion. I am King Porposeidon, and this is my wife Queen Shira.
Shira: We thank you for vanquishing those dreadful pirates! They've been attacking and plundering our city over and over again! None of our finest soldiers have been able to stop them all. So we've searched the seas for someone who can help us.
ChuChu: Kine and I were exploring when we discovered this place. We told them all about you, Kirby! So they requested us to bring you here.
Kine: The only problem was that you can't breathe underwater, much less swim as well as us.
Just then, the pink pearl floats down in front of Kirby.
Porposeidon: And we have the solution. You recognize this? It's the same one that turned you into what you are now.
Shira: It's also the reason why you can understand your friends.
Porposeidon: There are six more like this scattered across the oceans. Together, they're the key to unlocking an ancient weapon that will bring down the whole pirate armada! It's up to you to find them and bring them to us. Feel free to look around our city a bit, find anything useful before you set off on your quest.
Shira: Once you've completed your mission, we'll turn you back to normal.
ChuChu: You can count on us!
The three start to leave the throne room.
Kine: And so begins another perilous, yet awesome adventure of Kine and his sidekicks!
ChuChu: Oh, brother.
The scene fades to black. The next scene shows them swimming through a barrier reef.
ChuChu: So this is where that pretty pearl led us to, it's so beautiful here!
Kine: Well this ain't a vacation, and we're not here to sightsee. Hey Kirby, do you know how to use that thing?
Kirby pulls out the pearl and it starts glowing.
Kine: Lead the way.
The three begin to navigate their way through the reef. After a while, they enter an area where they see another pink pearl sitting on the ocean floor.
Kine: What do we have here.
Kirby moves slowly towards the pearl.
ChuChu: Be careful, this is usually the part where something big and dangerous comes along!
Kine: Oh please, like what scary monster would show up in a nice place like this?
Suddenly, a giant piece of coral rises up from the floor, revealing to have a face like Whispy Woods. It then opens it's mouth and inhales the pearl.
Kine: Hey, we called dibs on that first!
ChuChu: You got this, Kirby! We're rooting for you!
Kirby fights the boss. After he defeats it, it shows the same beaten look as Whispy Woods as it spits out the pearl.
Kine: That'll teach you! Say, doesn't that almost look like the apple tree that tries to hurt Kirby at the beginning of his adventures?
ChuChu: Oh yeah, why can't that mean old tree just leave Kirby alone! Anyway, we better get this back to them.
Kirby picks up the pearl and they all start swimming away from the reef.