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

Here’s a guide on how to get the Swivel Guns 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 automatically shred weak points and clear enemy decks during boardings, you need the Swivel Gun Ultimate Plan.

Here is exactly where to go and how to navigate the underwater cave system to grab it.

Prerequisites for the Swivel Gun 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.

First, complete Sequence 6, Mission 1. This will unlock the Diving Bell which will allow Edward Kenway to dive and explore underwater areas and underwater caves found throughout the map in Assassin's Creed Black Flag Resynced.

Devil's Eye Caverns Location and Coordinates

Once you have access to the Diving Bell, get on the Jackdaw and fly to the Devil's Eye Caverns. You will find this dive site on your map at coordinates (456, 332).

Sail your ship directly over the dive location marker on your map and stop the vessel. Interact with the Diving Bell to drop down into the water.

Finding the Chest

It can be hard to find your way through underwater caves because of limited oxygen, strong water currents and dangerous sea creatures.

Dive into the water at (456, 332), leave the Diving Bell and swim down the left side to find the entrance to the main tunnel. Follow the path into the tunnel and avoid the Sea Urchins on the rock surfaces in Assassin's Creed Black Flag Resynced.

As you turn right, a strong current will grab you and pull you forward. Ride the current while staying toward the right side. When you exit the current stream, look to the left to find a air pocket. Swim into it to completely refill your oxygen meter.

Head out of the air pocket toward the nearby shipwreck. Dodge the floating Jellyfish, swim through the ship opening, and re-enter the tunnel path beyond it.

Continue following the tunnel. You will pass a stream of air bubbles rising from the floor, which you can use to top off your oxygen if needed. Otherwise, turn left and keep moving forward until you spot three Jellyfish swimming together.

Make another left turn past the Jellyfish group and push through the final stretch of the tunnel. If you find yourself constantly running out of breath, you can temporarily open the game settings and disable oxygen depletion for unlimited underwater air.

Keep swimming forward until you break the surface inside a dry cavern. Climb up the stone ramp, turn left, and walk to the end of the passage to spot the chest. Interact with the chest to claim the Swivel Gun Ultimate Plan in Assassin's Creed Black Flag Resynced.

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 Swivel Gun upgrade.

FAQ

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

A. No. You will need the Diving Bell from Sequence 6, Mission 1 to enter Devil’s Eye Caverns.

Q. How do I avoid taking damage from sea creatures in the tunnel?

A. Observe the movement patterns of the Jellyfish and stay well clear. With Sea Urchins, simply hug the middle or the other side of the tunnel walls so as not to touch them.

Q. Can I turn off oxygen depletion in the game settings?

A. Yes. If the underwater section is too difficult, you can turn off the oxygen requirement in the game settings menu and explore the cavern without drowning.

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