From Monkey Island wiki
The Giant Manatee is the location of most of "Lair of the Leviathan", the third episode of Tales of Monkey Island, and later a helpful friend to Guybrush Threepwood. It first appears at the end of the previous chapter, "The Siege of Spinner Cay", where it swallows up the Screaming Narwhal with Guybrush, Van Winslow and Morgan LeFlay aboard.
The Manatee is attracted to the seahorse/turtle/fish creatures that can be summoned to lead the way to La Esponja Grande, which is found in the Manatee Mating Grounds. Long before swallowing the Narwhal the Manatee had swallowed another ship, the Howler Monkey, whose crew was also searching for the sponge. Later Guybrush can use the skull of one of the strange creatures to regain entry to the Manatee's insides and to call him to swallow the Howler Monkey once more.
The crew of the Howler Monkey enjoy living in the Manatee's belly and remove one of its cochleas (its inner ear) so that, without its internal sense of direction, it will never find the mating grounds. Meanwhile their captain, Coronado De Cava, believes his crew dead and lives in its throat, trying painstakingly to build a new cochlea out of thousands of grubs. During the group's stay in the Manatee, only Santino dies, and even then his crewmates don't seem to notice, especially Moose, who looks to Santino for advice.
Besides these two ships and their passengers, Murray also ends up inside the Manatee's belly and gets stuck inside a chest until Guybrush frees him.
Once the Manatee (now emptied of his passengers) reaches the mating grounds he finds that the sole female manatee, many times his size, attacks any possible suitors. Guybrush learns the languages of the manatees and uses the Tongue of the Manatee, a special device that lets him speak like a manatee, to woo her on the manatee's behalf so he can retrieve La Esponja from inside her cave. The two manatees are later seen swimming flipper in flipper.
Inside the Manatee's stomach there are pools of caustic, yellow bile, which will rise if bile sacks (such as the ones Noogie uses as bongos) are slapped steadily. The usual means of escape from inside the Manatee is to pour a special purgative into the bile pool, although Bugeye manages to escape (the second time) by swimming out while the Manatee is kissing its mate.
- In the PS3 version of "The Siege of Spinner Cay", after a cutscene with the manatee swallowing up the Screaming Narwhal, the player is automatically awarded a gold trophy labeled "The BIG Finish" at the very end of the chapter.
- There are also nine out of eleven trophies related to the manatee in "Lair of the Leviathan", all in the "PlayStation Network Trophy Achievements". These include:
- Bronze: Meet Murray (having Guybrush show Murray to everyone inside the manatee, including De Cava, prior to uniting Murray with Santino's skeleton); The 0.01 Percent Solution (Guybrush must give 10 out of 100,000 Manatee Throat Grubs, one at a time, to De Cava); Frequent Tuber (Guybrush goes through all three tubes on both ways before and after unclogging one of them with a mug of bile); I'm So Faced (he must use every facial expression he learned from Bugeye, Morgan, and other people and items in the Pirate Face-Off; Bongo Baby, Yeah (having Guybrush repeatedly play on Noogie's "bongos" prior to using the flopping fish on them)
- Silver: The Newlyfed Game (Guybrush must convince De Cava that the former is "married" to Morgan by correctly answering three of De Cava's questions in a row); There Is a Brotherhood of Jerks (Guybrush manages to get the Brotherhood to get a unanimous vote for him); La Esponja... Grande? (Guybrush manages to get the two manatees together and swim out of the cave where La Esponja Grande is)
- Gold: Feed the Beast (Guybrush manages to summon the manatee to re-swallow up De Cava and his remaining crew that are in the Howler Monkey)