Acro, who relocated on Aqua Star, gets possessed again when he somehow stumbles across a Crystal Shard in the water. The battle starts off much like the second phase did in Dream Land 3; Acro shoots out the same objects as before that must be shot back at him to cause damage. Now, however, Kirby has the luxury of inhaling them, and no longer needs to precariously shoot bubbles at them to send them back. Occasionally he will do an underwater back flip and crash into the ground, creating two rocks that can be inhaled and shot back.
After enough damage is dealt, Acro retires to the seafloor as the cavern crumbles. The screen beings to scroll upward as he chases Kirby to the surface. Kirby encounters more enemies to inhale as Acro darts round shooting out Pedos. After Kirby lands the finishing blow, Acro sinks out of sight, leaving Kirby the Crystal Shard.
Edit: One of my first papercrafts but definitely buildable. I recommend starting from the snout until you reach the last three pieces, consisting of the last body ring and the two tail pieces. Build the tail first, connect to the last ring, then finally glue those built 3 pieces to the main body.