This discussion may contain spoilers!
A list of things to try in Lair of the Leviathan.
Look at Morgan's head, wrist, boots, and sword instead of just examining the the part of her person as per Winslow's instructions.
Try using the sword on the attached cochlea.
Try giving the grub to Morgan.
Show your hook hand to Morgan.
Talk to Murray when he's in your inventory and you also have the grub in your inventory.
Try giving Murray to Morgan, the three pirates, and de Cava.
Show Murray the Festive Skull.
Show Murray the iron monkey cage.
Try throwing Murray in the pool of bile.
Try giving the picture of Guybrush to the three pirates.
Offer the seated Murray a mug of ichor and the picture of Guybrush.
Show everyone the seahorse head and the cochlea.
Offer the crown or doubloons to all the crewmembers as a bribe.
Talk to the manatee without the tongue or reading the book, with reading the book but not the tongue, and with the tongue but not reading the book.
Look at the mast with Morgan on the ship.
Try throwing the sponge to de Cava's ship or using it in the cannon. Try throwing the seahorse head at de Cava's ship without using the cannon.