This quest will be unlocked after completing the "Unmanned" quest. To start it, you must return to Nassau by any means - most easily using fast travel.
Edward explores the wrecked Spanish fleet with his diving bell.
Diving for Medicines
Quest stages of Diving for Medicines
1. Follow Blackbeard
Just follow Blackbeard. You will discuss the problem of the lack of medicine, where it can be found - and what is needed to get it.
2. Acquire a diving bell
Hints:
- Purchase one from the harbourmaster
- Adéwalé may know another way
If you have enough money (5,000 Reales), you can simply purchase the diving bell from the harbourmaster.
However, there is a way to get the diving bell for free. If you speak with Adéwalé, he will tell you about a group of freebooters who have a diving bell.
Hint:
- Find the pirate camp
The pirates' camp is located on the southern side of Nassau. Sail around the island - or simply go there over land. Five pirates are guarding the bell. Get rid of them in any way you prefer.
Once all the pirates are dead, simply approach the bell and interact with it.
3. Sail to Blackbeard's location
Sail to the location marked on the map. There, you will find Blackbeard's ship - with your old friend Stede Bonnet on board - as well as the shipwreck of the San Ignacio.
4. Find the medicine amongst the wreckage
Slowly sail up to the shipwreck in front of you - and drop the bell.
Underwater, watch out for jellyfish, as touching them causes damage, and keep an eye on your limited oxygen supply. Your crew will throw down air barrels that you can use to refill your oxygen meter.
Find and open the hatch leading inside the sunken ship, then swim below its deck.
After swimming inside, locate the chest with medicine and interact with it.
Unfortunately, this will cause the wreck to collapse - you won't be able to go back out the same way you came in and will have to escape through a different route.
5. Find a way out
The only escape route is an underwater tunnel, so swim into it and head straight. After a moment, you should see falling rocks and rising air bubbles. This marks a spot with an air pocket where you can refill your oxygen gauge.
When you reach the next larger cave, a strong water current will sweep you away. Your view will be blurry and the controls will be difficult, but try to maneuver using the directional keys to avoid hitting the rocks - as hitting them will cause some damage.
The current will carry you to the tunnel's exit and out into open water. In front of you, you will see a shark devouring a diving sailor, which hints at what you need to watch out for now.
6. Surface with Blackbeard's diving bell
The bell you need to reach is on the other side of the wreck resting on the bottom. To hide from the shark, you can use the seaweed growing on the ocean floor, or you can take cover inside the shipwreck.
Another way to move around without being spotted by the shark is to swim alongside schools of fish.
If the shark does take an interest in you, though, you can try to dodge its attack. If you mess up and fail to dodge the shark's attack, expect heavy damage - on normal difficulty, you can survive one attack, but you likely won't survive two.
When you reach the bell, swim inside and interact with it to surface. After the cutscene, this quest will end and the next one will be unlocked - Devil's Advocate.