There is this guy by the shore once you get your ghost hunting devices. Give him your hotel room key and hey will give you his boat key. Use it to travel to the lighthouse. :-)
To the shipwreck near the lighthouse.
go to the lighthouse.
go to the lighthouse but watch out for wind!
You go inside of it and you cant get knocked down by the wind.
go to the lighthouse and you will meet a ghost. he will say go north to the shipwreck. go to your boat and go to the top left corner. a light will be shining on it.
After you find the ghost in the lighthouse, go to the rocks where the ship sank and pick up the locket.
depending on the jail if you mean the one on conterfeit island you answer the detectives questions correctly if you mean the on on ghost story island you leave the prison and go to the lighthouse
go to the lighthouse, a little northwest of the main island.
At the shipwreck north of the rocks in the harbor. After your first visit to the Lighthouse, and to the prison, you will be summoned back to the lighthouse to see the Keeper. The lighthouse light will show the wrecked ship on the rocks. Leave the lighthouse and go there in the ship, and you will get the locket to return to Fiona.
On your first visit, climb the windy stairs and leave you Thermometer (it flashes) in the Keeper's Room. Then go do the prison if you haven't already, and return to the beach at the Inn. You will get a signal from the thermometer to go back to the lighthouse.
go to poptropicasecrets.com and select Ghost Story Island. there is a video walkthrough
You go to Steamworks and head to the museum and there is the Deogen