The 3 sisters wiped from the 11th floor of Luigi's Mansion 3 hotel, we are going to the pirates floor. But you will soon realize that a boat carcass is blocking the entrance. To initiate a dialogue with Professor Elvin Gadd , look through the ship's hole on the right. As you come out of there, the Virtual Boo will ring and the teacher will tell you that he has a new object to share with you, in the boiler room. Back to B2 to collect this improvement.
Many ghosts and a garbage will block your way to the main room. Remember, the ghosts can equip helmets or buckets, and they can be undressed with a ZL+ZR. Once in the main room, go to the storage room at the bottom left. Remove all the boxes that block the way and let Gooigi through.
Once Gooigi is on the other side, switch to Luigi and operate the valve, stopping the stream that separates our gooey friend from a cardboard containing a Toad.
To get it out of there, vacuum it and aim to get it to the other side. A big ghost blocks the exit, so you'll have to improvise.
The box containing the fan has disappeared in the main room, but you only need to place two team members on the two ground buttons to make it reappear. Put Luigi on the bridge with the Toad, then go to Gooigi and move the bridge again so that you can access the platforms on the right. The item is stuck just above you. Take the Toad again in your hose, then eject it against the object that will then fall into your hands.
Come back near Gooigi, suck Toad back in and throw him on the blocked ladder to the far right of the room. Climb it and walk back through the corridor that you crossed with a buoy on your first visit to the boiler room. Enemies will jump at you and even take poor Toad as a shield, and as usual, ZL+ZR is your best friend.
Come back to the room that let you lower the water level, but this time break the wall on the far left thanks to Toad's head. As you walk through the unblocked conduit, Toad will be tossed again. Aspirate it, then aim so that it reaches the button unlocking the door.
Break the wall containing white bricks to reveal two plates to activate, launch Toad on the high one. This will reveal a new blade to blow in order to move the footbridge upwards. Let Gooigi blow and climb on it with Toad to reach the next door. A small blow on the ladder that prevents you from returning to the first room.
Clean the room and go back to basement B1 so the Professor can install his new equipment. It's time to go clean up on floor 12!
Once back on the pirate floor, plug the Poltergust into the spectral socket at the far left at the back of the room. The overpower of the Poltergust allows you to shatter the decor: turn it all around until you can reach the big swing door. Enter, walk along the entire restaurant, up to a new door and an improvised beach under a deserted dome on floor 10. Ring the bell and wait for the boat, get on it, and the boss fight can begin.
Floor 12: The Spectral Catch Boss
The big ghost shark will blend in with the floor to attack you, and ghosts throw barrels of explosives at you. For this first phase, grab the barrels and throw them into the monster's mouth when it is open. Repeat the process until the shark comes out of the ground and attacks you. Always stay in motion and wait until he throws a big loaded attack that he will let him crash into the floor. This is the perfect time to attack him. Repeat this phase again and once he is at 100 life points, he will change his strategy.
On the far right of the arena will appear a target: quickly shoot a suction cup on it and pull it up, the boss will knock over the boat to try to eat you. Once back on the floors, repeat the same operation you performed when the shark was on the ground, but allow a little time between receiving the barrel and sending it, otherwise you may find the mouth be closed when you send it.
Once he has the mouth full of gunpowder, the shark will come out one last time. You know what you have to do.