While exploring Stranglethorne, I found a bottle washed up on the beach.
Inside was a message from someone held captive by a great beast on an island. The note says that they can see the mainland to the northwest, and there's an island to the southeast of where I found the bottle, so I swam across to see if I could find the author of the note.
I found a tauren lady held captive on the island, and indeed, she was the one who wrote the note. She introduced herself as Princess Poobah, and, while grateful that I had come to rescue her, she insisted that I recover her stolen belongings before we left. It seems that the local primates had taken a liking to some of her shinier trinkets.
After recovering her baubles, Poobah finally agreed to tell me who had the key to her shackles - an enormous ape named King Mukla.
With Mukla defeated, all that was left was to unlock Poobah, build a raft, get her safely back to Booty Bay, and listen to her complain about how my raft leaked and her feet got wet until I finally dropped her off.