Clem

Clem is the tenth boss encountered in Luigi's Mansion 3, a mechanic in Basement 2 who guards the Floor 10 elevator button.

Appearance
Luigi initially encounters Clem while the latter is napping. However, before Luigi could sneak away, he accidentally steps on a rubber ducky, causing Clem to stir, and then activate a pipe to spray Luigi as a prank before fleeing, forcing Luigi to stop the release of water.

He later encounters him in a large reservoir, where Luigi again attempts to avoid waking him, only to end up stepping on a rubber ducky yet again, waking him. Clem gets irritated, but then gets the idea to fill the reservoir. However, after Luigi gets into an inner tube and saves himself, he decides to confront Luigi personally.

Battle
Clem will attack the player with a paper fan as well as launch mines.

The player needs to manipulate Clem into spinning himself in circles with his fan, then suck the inner tube he's on and launch it into one of the sides of the reservoir, causing it to deflate. Afterwards, the player needs to disembark and approach his prone body. If he regains consciousness, he'll be busy putting on another inner tube, requiring the player to flash him as he's busy and then try to suck him in (though it's preferable to use Gooigi and have him suck Clem in while Luigi stays inside the pool). Upon being defeated, Clem will struggle to free himself before being sucked in, humorously releasing several rubber duckies in addition to the floor 10 button which falls into the pool, requiring Luigi to drain the reservoir to get the button.