The Broadside Cannons Number Ultimate Plan is in a secret underwater chest at The Blue Hole shipwreck in Charlotte, reached through the Diving Bell activity after you unlock diving.
This plan is one of the high-end Jackdaw blueprints in Assassin’s Creed IV: Black Flag. Once you have diving available, the pickup itself is short: go to The Blue Hole, descend with the bell, follow the wreck route, survive the shark prompts, and loot the hidden chest.
- Broadside Cannons Number Plan location
- Requirements to find Broadside Cannons Plan
- How to get Broadside Cannons Number Ultimate Plan in Assassin’s Creed IV: Black Flag
- Blue Hole mistakes that waste the run
- Using the Broadside Cannons Number Plan
- Jackdaw upgrade goals to chase next
- Frequently Asked Questions
Broadside Cannons Number Plan location
| Detail | Info |
|---|---|
| Plan name | Broadside Cannons Number Ultimate Plan |
| Activity | Diving Bell |
| Location | The Blue Hole shipwreck, Charlotte |
| Coordinates range/site locator | The Blue Hole in Charlotte; map readouts appear around 440,145, 437/438,145/144, or 471,170 |
| Prerequisite | Diving Bell unlocked through story progress |
| Chest position | Deep far end of the dive, under or inside broken overturned ship wreckage |
| Hazards | Two shark attacks, plus air pressure from the long swim |
| Reward | Blueprint for the final Jackdaw Broadside Cannons Number upgrade |
KEY!Use The Blue Hole as your main locator, not a single coordinate readout. Map coordinates for this dive site can appear slightly differently, but the named Charlotte Diving Bell site is the target.
The reward is the blueprint for the final Broadside Cannons Number upgrade on the Jackdaw.
Requirements to find Broadside Cannons Plan
You need the Diving Bell before The Blue Hole can be used. Keep progressing the main story until the diving system has been introduced, then return to the open world and sail for the Charlotte dive site.
If the bell activity is not available yet, the chest is not reachable from the surface. The plan is underwater, so this is not a collectible you can grab early by swimming from the Jackdaw.
How to get Broadside Cannons Number Ultimate Plan in Assassin’s Creed IV: Black Flag
This route takes you from the world map to the secret underwater chest that holds the Broadside Cannons Number Ultimate Plan.
STEP 1/6
Open the map
Open the world map, and use fast travel if you have already visited the area.
STEP 2/6
Select The Blue Hole
Choose the bell icon in the southwest part of the map labeled The Blue Hole.
STEP 3/6
Enter the Diving Bell activity
Arrive at the marker and enter the bell activity to descend underwater.
STEP 4/6
Follow the wreck route
Swim through the broken ship and wreckage, keeping to the route that leads toward the secret chest.
STEP 5/6
Dodge the first shark
After passing through the broken-down ship, wait for the white flash and dodge the first shark attack.
STEP 6/6
Loot the secret chest
Dodge the second shark right before the chest, then open the secret chest to claim the plan.
Video help
Blue Hole mistakes that waste the run
The easiest mistake is opening an ordinary chest and leaving too soon. The Blue Hole contains more than one chest, but the plan is in the secret one tucked at the deep far end of the wreck route.
Air is the other problem. Start with a full air meter, refresh when the route gives you a chance, and avoid wandering around the open water after you pass the broken ship. A slow search can turn this short pickup into a failed swim.
Do not chase the coordinate numbers too literally. If your map readout is a little different, stay focused on the The Blue Hole Diving Bell icon in Charlotte.
Also, do not expect the blueprint to appear at a harbor first. The harbourmaster sells the upgrade only after you loot the underwater chest and add the plan to your ship blueprints.
Wait for the white flash before dodging each shark; dodging early is what usually gets Edward caught during the final swim to the chest.
Using the Broadside Cannons Number Plan
After you open the chest, the blueprint is added to Ship Upgrades. From there, visit a harbourmaster to buy the final Broadside Cannons Number upgrade for the Jackdaw.
Jackdaw upgrade goals to chase next
The Broadside Cannons Number plan is one of the Jackdaw’s Ultimate or Elite ship plans. After this pickup, the natural next targets are all Ultimate Plan locations, especially Swivel Guns, Round Shot Strength, and Heavy Shot Strength.
You will also want a steady route for Reales and Metal, because the late Jackdaw upgrades become expensive fast.
Frequently Asked Questions
Where is the Broadside Cannons Number Ultimate Plan?
It is at The Blue Hole shipwreck in Charlotte, inside a secret underwater chest reached through the Diving Bell activity.
Do you need the Diving Bell first?
Yes. The Blue Hole chest is part of a Diving Bell location, so you must unlock diving through story progression before you can go after it.
Which chest at The Blue Hole has the plan?
It is the secret chest near the deep end of the wreck route, below or inside the broken overturned ship section, not one of the easier side chests.
What are the correct coordinates for The Blue Hole?
Use the named The Blue Hole bell icon in Charlotte. If your coordinate readout differs slightly, the dive-site name matters more than matching the numbers exactly.
How do you avoid the sharks during the dive?
There are two shark attacks on the chest route. Keep moving, wait for the white flash prompt, then dodge instead of mashing early.
More questions⤵
Why can I have the plan but still not buy the final upgrade?
The plan only satisfies the blueprint requirement. In Resynced, the highest-tier ship upgrades may still need the right harbourmaster progression, plus the required 20,000 Reales and 650 Metal.
Leave a Reply