Help Sharky defeat the killer whale. On your way, you will meet other enemies that hurt you. Jellyfish can be hit with your bubble attack. Pufferfish can be hit with a fin attack.
Collect poisons on yout way to hurt the killer whale more. You can use your posioned bubbles when you reach the killer whale. If your poisoned bubbles are Empty, you can use the bubble attack, but it will makes less damage.