Assassin's Creed Black Flag Resynced packs a lot of upgrade plans across the Caribbean, but the Fire Barrel Strength Ultimate Plan is one that players consistently miss. Unlike plans you pick up from shops or enemy drops, this one is buried. Literally. You need to dig it up from a treasure cache in the southern region of Cruz, near the cave of San Juan. Here's exactly where to go and what to expect.
Where is the Fire Barrel Strength Ultimate Plan?
The Fire Barrel Strength Ultimate Plan is a buried treasure item, which means you won't stumble across it during a standard mission or by looting an enemy. You need to actively seek it out using the map coordinates system.
Head to the cave of San Juan in the southern part of the Cruz region. The two coordinates you need are (454, 462) and (455) in that area. Once you reach the marked spot, you'll be able to dig up the treasure cache containing the plan.
San Juan treasure dig site
How to reach the Cruz region
Cruz is accessible by sailing the Jackdaw south from your starting areas. Keep an eye on enemy patrol ships in the region before you dock, especially if you haven't cleared nearby forts yet. Getting into a naval skirmish right before a treasure hunt wastes time and resources.
Once you're ashore, follow the coastline toward the cave entrance. The dig spot is close to the cave coordinates, so you won't need to venture deep into hostile territory to grab it.
Cruz region map overview
Why does the Fire Barrel Strength plan matter?
Fire barrels are one of Edward's most effective tools for dealing with pursuing ships. Upgrading their strength means enemies take more damage when they sail into the barrels you drop behind the Jackdaw during a chase or combat engagement. The Ultimate Plan tier represents the highest available upgrade for this ability, so tracking it down pays off significantly in tougher naval encounters later in the game.
What do you need to dig up treasure in AC Black Flag Resynced?
Buried treasure in AC Black Flag Resynced doesn't require any special tool beyond reaching the correct coordinates. When you're standing on the dig spot, the game prompts you to interact and Edward automatically unearths the cache. The Fire Barrel Strength Ultimate Plan comes out as a crafting plan item that unlocks the upgrade tier in your menu.
Getting the most out of your fire barrels
Once you have the Ultimate Plan unlocked and crafted, fire barrels become a reliable tool for breaking off pursuits and punishing aggressive enemy captains. Drop them in tight waterways where enemies have limited room to maneuver, and combine them with the Jackdaw's broadside cannons to finish off damaged ships quickly.
For more on building out Edward's combat capabilities, the AC Black Flag Resynced best build and loadout guide covers weapon choices, trinkets, and crafting upgrades in detail. If you're still working through the early game, the essential tips for what to do first will help you prioritize the Jackdaw upgrades and officer unlocks that matter most before you start hunting plans like this one.
Jackdaw fire barrel deployment
Other buried treasure worth tracking down
The Fire Barrel Strength plan isn't the only reward hiding under the soil of the Caribbean. There are buried treasure chests scattered across the map with Reales, resources, and other upgrade materials. If you want a full breakdown of every dig site, the complete treasure map locations guide has exact coordinates and reward lists for every cache in the game.
For everything else the game has to offer, the full AC Black Flag Resynced strategy guides collection is the best place to keep building out Edward's arsenal and the Jackdaw's firepower.