After swimming through the ocean for about four hours, they reached a huge underwater city.
    "This is the Marine City," said Sashimie, "We'll rest here."
    Luigi rested at the Marine Motel for a day since he was tired of swimming through the ocean.
    When he woke up he heard ruckus going on outside.
    "You better worship the Great Emperor!" yelled a voice, "Or we'll keep the Ocean Star for a little bit longer!"
    "We refuse!" said another voice, "Even if we all die out in confusion, at least we didn't die worshiping him!"
    Luigi decided to peek out the window. He saw a beast outside of the motel. It had a fish's tail and two human hands. It could have been a merman but its head was a fish! It held a golden trident in its hands.
    "Wake up!" cried Luigi shaking Sashimie, who was still asleep, "Someone's outside!"
    Sashimie woke up and also peeked out the window. When she saw who it was she gasped, "Lord Neptor! He's arguing with the mayor again!"
    "So that's Lord Neptor," said Luigi, "He doesn't look that threatening except for his trident."
    "You'll be surprised," said Sashimie, "He killed about ten fish just by punching them."
    "Let's go get him!" said Luigi.
    As soon as Lord Neptor left the city, Luigi and Sashimie followed him into the Undersea Palace. The entrance of his palace was magnificent. It had huge golden fish statues lined along the walls. The hallway, however, was dark. The entered the next room not knowing that a fish was spying on him.
    The fish reported the news to Lord Neptor.
    "What?" he exclaimed, "A plumber and a fish entering my palace? I cannot allow that! Cheep-Cheeps! Get him in the next room!"
    The next room wasn't underwater but had two water pools in the center. Then, without warning, Cheep-Cheeps flew out of the two pools. They dived at Luigi and Sashimie and started bouncing around the room. The bouncing fish soon cornered Luigi.
    "Help Sashimie!" cried Luigi.
    "Watch this," said Sashimie and she shot a beam of ice out of her mouth.
    All of the Cheep-Cheeps froze.
    "Let's move to the next room," said Luigi, "Oh! And thank you for saving me!"
    The next room was empty. There weren't even any pools of water.
    "I have a bad feeling about this room," said Luigi, "I have a feeling we're about to be attacked."
    "You've got that right!" exclaimed a voice.
    The two Crustacean Bros. appeared from nowhere.
    "We've upgraded our shells!" said the red one, "Now we're resistant to anything!"
    "Don't even try and flip us over!" said the blue crab.
    Luigi smashed his hammer on the blue crab's back but it did no good.
    "We told you so!" said the blue crab, "Now take this!"
    The blue crab shot a barrage of acid bubbles at Luigi. The bubbles hurt Luigi.
    "Ha! That's for breaking our other shells!" said the blue crab.
    "Wait!" cried Luigi, "I know what to do!"
    He grabbed the blue crab's leg and threw him upside down.
    "No! He found a weak spot!" cried the blue crab.
    Luigi pulled out his hammer and smashed the blue crab's belly.
    "No!" cried the blue crab and his body went to pieces.
    "No! Brother!" wept the red crab, "You'll pay!
    The red crab became redder than ever and he started scampering across the room like a crazy crab. Luigi couldn't even catch him since he was going way too fast.
    "Now time for an acid bubble attack!" said the red crab.
    "Take this!" cried Sashimie and she shot another ice beam at the red crab before he could attack. The red crab froze and Luigi flipped it over and did the same thing that he did to the blue crab. Both Crustacean Brothers were killed for good.
    "Yeah! We did it!" exclaimed Sashimie.
    They entered the next room.
    The next room was completely submerged underwater. The door ahead was locked. There were four switches laying on the floor.
    "I guess we have to press the switches to open the door," said Luigi.
    "Yeah, but look!" exclaimed Sashimie.
    Sashimie pointed at Unagi the Eel. His teeth looked about as big as Luigi's arm! Luckily, he was asleep.
    "Ha!" laughed Neptor, "They will surely be his lunch if he wakes up!"
    Luigi entered the water careful not to wake Unagi and pressed the first switch. The next switch was right next to Unagi's left side. Luigi quietly pressed the button. The next one was right in front of Unagi's mouth! But Luigi pressed it without him waking up. The finally switch was underneath Unagi himself. Luigi carefully moved Unagi's huge body and pressed the switch. The sound of the rusty door opening made Unagi awaken!
    "Shoot!" cried Luigi and he tried to swim away.
    Unagi lunged at Luigi but the plumber barely dodged. Luigi grabbed his hammer and smashed Unagi's face. Unagi cried in pain but he soon grabbed Luigi before he could reach the door. His Oxygen Mask fell off and he couldn't breathe.
    "Help!" cried Luigi but only bubbles came out.
    But Sashimie knew what she had to do. She dived underwater, retrieved the Oxygen Mask, and threw to Luigi. Luigi put it on and smashed Unagi in the face again with his hammer. The force of the blow knocked Unagi out.
    "Thanks again!" said Luigi.
    Then, they entered the next room, the throne room.