The Caribbean is a dangerous place to sail in Assassin's Creed: Black Flag. From rogue waves to giant cyclones to an armada of hostile ships, you'll need to improve your own boat as much as possible if you want to survive.

There are a lot of upgrade options for the Jackdaw, some of which are infinitely more important to acquire than others. One of those is the Heavy Shot Storage Ultimate Plan, which will maximize the damage this alternate ammo type can do. Given the Heavy Shot is one of the best ways to deal a ton of burst damage to close-range targets, getting this upgrade should be a top priority once you start venturing to the higher difficulty regions.

Heavy Shot Storage Ultimate Plan Location

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Unlike a lot of the other Ultimate Plans, the Heavy Shot Storage one isn't actually tied to any diving section in the game. Instead, this plan is hidden away in a Treasure Map you can easily miss if you're not looking around for collectibles. To start, make your way south to Cayman Sound, which is in the Castillo de Jagua region.

Found at coordinates (302,311), park your boat and head onto the island. Once you're on land, head to the farthest northwest corner of the island. Specifically, go to coordinates (298,310) and look for a couple of destroyed crates and barrels with a skeleton in front of them. Interact with the skeleton to obtain the Petite Caverne Treasure Map.

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Now that you have the map, head east to the region of Punta Guarico and then go to coordinates (864,237) to find Petite Caverne. Similar to other caves, this one is occupied by a ton of hostile pirates you'll need to deal with. When you arrive, fight or sneak past the pirates to the back of the cavern at coordinates (863,235).

You'll want to look for a small campfire with a plank bridge to the right and a waterfall behind it. Go towards the waterfall and head behind the large stalagmites to find a couple of shovels leaning against the wall above a small dirt spot. This is where you will dig up the treasure chest containing the Heavy Shot Storage Ultimate Plan.

How To Unlock The Heavy Shot Storage Ultimate Plan

In order to actually use the plans you've acquired, you'll need to purchase the upgrade at the Harbourmaster. To do this, you'll need to ensure that this vendor has been completely upgraded. This can be done at the Great Inagua by talking to the man right outside the Harbourmaster's stall. Upon speaking with him, you'll have the option to improve this vendor by spending a few thousand Reales.

Once the Harbourmaster is fully improved, talk to any of these vendors throughout the game and select the "Upgrade Ship" option. This will take you to a menu where you can pick which parts of the Jackdaw you want to increase the power of. Heavy Shot Storage can be found in the top left corner under the "Weapons" category.

To upgrade the Heavy Shot Storage to the max level, you'll need:

  • 25,000 Reales
  • Heavy Shot Strength Ultimate Plan

I do recommend snagging this upgrade when you can, as the Heavy Shot is one of the best ways to consistently deal a high amount of damage to close-range targets. You'll heavily rely on this throughout all stages of the game, which makes increasing its overall damage by an additional 67 percent extremely useful when fighting ships such as Man O' Wars or even the Legendary Ships.