Do NOT hunt in the Carribean. You will be lead into a deathtrap.
Enter The Big House on Hispanola and kill Jacques. GET the shiny brass KEY from Jacques' CORPSE. UNLOCK DESK. OPEN DESK. GET MAP DESK.
Go to the Tavern on Tortuga. BUY BOUCAN. Go to Ghislene, Levassier's cook. GIVE BOUCAN COOK. She cooks it up and returns it to you in a basket.
Find the hermit on Hispaniola. GIVE BASKET HERMIT. He will eat the boucan. ASK HERMIT HELP. GIVE MAP HERMIT.
Go to the waters south off of Redbeard's isle. Go down and GET KEY, the key will be in a random room down here. Dive to the lowest depth. (the passage seemed to be closed until midnight).
Go into the tunnel to the sunken ship. KILL OCTOPUS [it is tough!!!]. The questor must land the killing blow. UNLOCK CHEST. GET CROWN CHEST.
You now have 3 options to get your reward and whois:
Give the Crown to the Spanish Admiral: You get his thanks, and that's it. In addition, all the French boucaniers now hate you. (Don't choose this option.)
Give the crown to Msr. Levassier: You get a pearl-handled dueling pistol!
Give the crown to the captain of the ship in the harbor: You get a huge pearl!