Assassin's Creed 4: Black Flag Walkthrough Part 31 – Sequence 6: “Diving For Medicines”

Optional Objectives:
Loot 3 Treasure Chests
Avoid being attacked by a shark

Head on over to Nassau when you are ready to move forward and into the next sequence. Be sure you have lots of Reales (5,000 minimum) so you can start the next mission. Follow Thatch to start as he explains the new situation growing around Nassau.

Head on over to the Harbour Master after the walk. Go into the upgrades menu and buy the Diving Bell for 5,000 Reales. Take a little time to upgrade anything else after that on the Jackdaw. The more upgrades you have now, the better off you will be in future naval engagements. When done upgrading, head on over to the Jackdaw. Grab the wheel and you are off. Time to make for the diving location: San Ignacio Wreck.

When you make it there it is time to make your first deep dive. This can be a very short dive if you just want to get the objective, but there are some plans here, animus fragments and chests to be found as well.

For those after loot, start swimming down from the diving bell. Just a bit to the left, on the sea floor you will find the first chest. Grab it. Now head toward the the opening in the ship's hull with 3 Jellyfish in front of it. Avoid the Jellyfish as they will sting you and do damage. Go inside and grab the next chest. Exit the hull and look just past this part of the wreck. You will see a mast sticking out. About the yardarm you will spot an Animus Fragment. Grab it and turn to the West. First, go to the more Northern of the pair of chest. Head to the Northern end of the wrecked ship and head through the opening. You will see a chest. Now go to the second one, closer to the start, where you will find a hatch to raise. Go inside there and you will see a chest with a beam across it. Interact with it to get the medicines you are after. Some the wreck will collapse, forcing you to find another way out.

Head through the opening ahead of you. Just swim through the cave until you find an air pocket. Take a moment to refresh Kenway's breath then dive back underwater. Just press on forward after that. You will see another diver. Unfortunately, they do not notice a shark in time. Watch as the shark snaps them up. Go into the seaweed below you. This is your Stalking Zone, giving you an escape from the shark.

While you can finish the memory right now and fully synch it, there is still a very important upgrade just ahead: The Elite Hull for the Jackdaw. Wait for the shark to swim South of your location. At that point, start swimming for the ship hull in front of you. Go inside it to find an Animus Fragment. Grab it and then duck into the seaweed. You only have a few things left to go. If you are running low on air, either return to the Air Barrel that was nearby the exit of the cave or head for the second diving bell. Just refill your breath there but do not follow the prompt to return to the surface.

Go to the South from the second Diving Bell and hide in the seaweed when the sharks are away. This will let you easily grab the chest there. After that you will want to head head to the West. There you can find the final chest and Animus Fragment.

Swim carefully over to the chest to avoid the sharks. Just next to the Chest is the final Animus Fragment. Grab them both then head back to the Diving Bell and surface in it.