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

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

Game Guide by Ragib Rawnak on Jul 21, 2026

Upgrading the Jackdaw is one of the best parts of Assassin's Creed Black Flag Resynced, and maxing out your firepower makes naval combat much easier. If you want to rain heavy explosive fire on enemy ships from a long distance, you need the Mortar Ultimate Plan.

Here is exactly where to go and how to grab it without getting lost underwater.

Prerequisites for the Mortar Ultimate Plan

Before you set sail, you need to make progress in the main story. You cannot get this upgrade plan right at the start of the game in Assassin's Creed Black Flag Resynced.

First, complete Sequence 6, Mission 1. This unlocks the Diving Bell, allowing Edward Kenway to explore underwater shipwrecks all over the Caribbean.

Antoca Wreck Location & Co-ordinates

Once you’ve gained access to the Diving Bell, head on the Jackdaw and sail towards the Antoca Wreck. You’ll find this sunken ship on your map at (600, 635).

Sail your ship directly over the wreck marker on your map and stop the vessel. Use the Diving Bell to dive down into the ocean depths.

Finding The Chest

Finding underwater shipwrecks in Assassin's Creed Black Flag Resynced can be tricky due to limited oxygen, low visibility and sea predators.

Once you drop into the water at coordinates (600, 635) leave the Diving Bell and face forward towards the path. Start swimming along the right side following the path deeper into the area.

When swimming along the right side watch out for a Shark swimming near. Keep moving along the path to avoid getting caught.

Keep on swimming till you find the ship wreckage. Inside there is a chest. Swim to the chest and open it to get the Mortar Ultimate Plan.

After opening the chest, the plan goes directly into your inventory. You can then visit a Harbourmaster or access the Jackdaw upgrade menu in your captain's cabin to buy the final mortar upgrade in Assassin's Creed Black Flag Resynced.

FAQ

Q. Can I get the Mortar Ultimate Plan before Sequence 6?

A. No. You must get the Diving Bell in Sequence 6, Mission 1 to reach the underwater chest at the Antocha Wreck.

Q. Do I have to battle the shark to get the chest?

A. No. You can swim past the Shark by staying along the right wall and moving steadily toward the chest.

Q. Can I upgrade the mortars immediately after finding the plan?

A. If you have enough Reales and resources, and you have already bought the previous mortar upgrades in the ship menu, then you can buy the upgrade right away.

Also, check our Assassin's Creed Black Flag Resynced Review and other guides below: