Find the author of the message at Jaguero Isle in the Cape of Stranglethorn.
Inside the bottle you find a note which reads, in fairly good handwriting:
<To any that can aid me->
<Please, my need for help is dire. A great beast holds me captive on an island in the South Seas.>
<The stars at night are foreign to me and obscured by the jungle trees, but on the clearest days I see shoreline to the northwest, and what seem to be large sailing ships to the southwest.>
<I beg of you, my would-be savior, please help me.>