For this achievement to unlock you need to find the wrecked merchant boat from a Lost Shipment Voyage, without uncovering all the clues you normally find along the way.
To start this quest you have to be at least rank 25 with the merchant alliance, buy a Lost Shipment Voyage at the merchant (the voyage with the fish and book), and start the quest by proposing it at your ships table.
When you have started the quest, you get a map with a route which the dissappeared ship supposedly has been taking. Look at your map on your ship, and start following this route while watching for flying crowds of seagulls above the sea. These seagulls indicate something of importance is floating in the sea. Stop at the seagulls, take a dive to check if there is a sunken galleon, and if not, sail further along the route. (ignore merchant chests and blue clue bottles if you come across them)
Once you have found the sunken merchant ship, dive to the boat and search for a very stylish skeleton with a book. Pick up the book and everyone in your crew will unlock the achievement.