Assassin's Creed Black Flag Resynced Guide | How to Get Hull Armor Ultimate Plan

Here’s a guide on how to get Hull Armor Ultimate Plan in Assassin's Creed Black Flag Resynced.

Game Guide by Ragib Rawnak on Jul 21, 2026

Upgrading your ship is the best way to survive high-seas battles in Assassin's Creed Black Flag Resynced.

If you want your ship, the Jackdaw, to take heavy hits from British and Spanish warships, you need the Hull Armor Ultimate Plan. Without this blueprint, your ship defense stays capped.

Here is where to find the plan, what you need before starting, and how to reach the chest safely.

Prerequisites Before You Start

You cannot grab this upgrade right at the beginning of the game. First, you need to unlock the Diving Bell by completing Sequence 6, Mission 1 (titled Diving For Treasure).

It is also smart to make sure the Jackdaw is strong enough to travel open waters safely around the middle portion of the map in Assassin's Creed Black Flag Resynced.

San Ignacio Wreck Location and Coordinates

Once you have the Diving Bell, open your world map and set a custom mark for the San Ignacio Wreck located at coordinates (348, 745).

Sail the Jackdaw directly over the marker. Stop your ship and interact with the Diving Bell to drop down underwater.

Guide to the Upgrade Chest

As you navigate the underwater terrain you might find yourself a bit confused by the limited air supply and aggressive wildlife. Exit the Diving Bell and survey the sea floor until you come across a natural rock arch. Swim directly under the archway to begin your route.

After passing the arch, keep close to the left wall. Following this left ledge leads you straight toward the target area. Keep an eye on your air meter and use air barrels if you start running low.

A Bull Shark patrols this area, so try to avoid swimming in open water near its path. Stay hidden by using the tall sea grass on the left wall. If it spots you, complete the quick time event to escape with minimal damage in Assassin's Creed Black Flag Resynced. Near the end of the left path you will see a broken piece of ship wreckage lying on the seabed. Swim inside the broken wood section to find a glowing treasure chest. Interact with it to claim the Hull Armor Ultimate Plan.

FAQ

Q. Can I get the Hull Armor Ultimate Plan without the Diving Bell?

A. No. The chest sits deep underwater at the San Ignacio Wreck. You cannot dive deep enough on your own, so you must unlock the Diving Bell in Sequence 6, Mission 1 first.

Q. How much does the final Hull Armor upgrade cost to craft?

A. After finding the plan, open your ship upgrade menu aboard the Jackdaw or at a Captain's Cabin. Crafting the final armor level requires 15,000 Reales and 1,500 Metal.

Q. What should I do if sharks keep killing me underwater?

A. Stay near the sea grass to remain unseen. If a shark attacks, use the on-screen button prompts to fight it off, then swim rapidly to the closest hiding place or air pocket.

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