Note: In order to access these treasure maps and chests, you’ll need to be online with UPlay and be using the Kenway’s Fleet portion of Assassin’s Creed 4: Black Flag.
There are three maps and chests that are only accessible through the Kenway’s Fleet portion of AC4. To access these chests, you’ll first need to finish the required missions (they’re listed under each chest) and gain the required treasure map. Here is more information on how to properly use Treasure Maps.
Chest 679, 381
To access this treasure map, you’ll need to complete The British Colonies: The Empty Cellar. This chest is located at the Northern tip of Cumberland Bay and it contains 4,000 Reales.
Chest 502, 44
To access this treasure map, you’ll need to complete Eastern Canada: Scarlatina. This chest will be located on the Southern Bay of Isla Providencia, near a shipwreck on the shore. This ship contains the Elite Fire Barrel Storage.
Chest 621, 277
You’ll need to complete Barcelona: Great Reputation II to access this treasure map. The chest is located near the Smugglers Den in Anotto Bay, near a ladder. This chest contains 4,000 Reales.
Not what you’re looking for? Check out the complete Assassin’s Creed 4: Black Flag Guide Index.