Captain Fishook

Captain Fishook is the thirteenth boss encountered in Luigi's Mansion 3, who haunts The Spectral Catch and guards both the thirteenth floor's elevator button and the yellow Toad's portrait. He is one of three non-humanoid bosses in the game, the others being Polterkitty and King Boo.

Appearance
Captain Fishook is a ghostly great white shark wearing an eyepatch which conceals the thirteenth floor's elevator button, his “good eye” being red and pupilless. He has a golden earring on his dorsal fin, his right fin is replaced with a hook-like scythe, and he appears to have a golden tooth.

Captain Fishook appears shortly after embarking on his ship, swimming up on the side behind Luigi. After leaping aboard, he reveals the thirteenth floor elevator button underneath his eyepatch before possessing part of the ship's deck, warping it into a semblance of his own visage.

Battle
Fishook will start by possessing the deck of his ship, attempting to suck in Luigi from below as Oozers throw powderkeg bombs from above. To force Fishook out of the deck, Luigi must push three powderkegs into his open mouth as he attacks. Afterwards, Luigi needs to evade Fishhook's scythe and lunging attacks, and specifically time his Strobulb flash so that it affects Fishook's right eye (as his left eye has an eye patch), giving Luigi the chance to attack.

When his HP is reduced to 100, Fishook will change tactics and possess his ship's quarterdeck (where the Toad's portrait is), raising the ship ninety degrees backwards in an effort to drop Luigi into his gaping maw. Luigi must use the Suction Shot on a board with a bullseye icon near the ship's bow to avoid the attack. Once the ship is level once more, the Oozers begin throwing powderkeg bombs from above Fishook in groups of four while the boss intermittently opens and closes his mouth; Luigi must fire six powderkeg bombs into Fishook's mouth to force him into the open. After taking three hits from the powderkegs, Fishook will tilt the ship again, with the board now moving left and right to make it a harder target.

After being exposed for the final time, Fishook gains an attack where he jets through the deck of the ship trying to bite Luigi; this can be dodged by bursting. Upon defeating him, he will struggle to flee only to be forced in downward as Luigi mimes reeling in a fishing rod. Upon Fishook's defeat, Luigi will obtain the thirteenth elevator button before Polterpup lowers a ladder to the quarterdeck, which Luigi can climb to find a pile of coins and release the yellow Toad from his portrait.

Trivia

 * Captain Fishhook, Ug, and Amadeus Wolfgeist are the only boss ghosts that posses objects in order to fight Luigi.
 * The cutscene before the boss fight with Captain Fishhook is a reference to the 1975 film Jaws.
 * When Luigi defeats Captain Fishhook, he will "reel" his Poltergeist as if he caught a fish.