Assassin's Creed 4: Black Flag Walkthrough Part 70 Shipwrecks & Caves: “Antocha Shipwreck”

Swim into the wreckage to the right to find the first of the treasure chests in the area. Be mindful of the seaweed as there is a Moray Eel living inside it. Just keep some distance and you will be fine. Swim out the back of the wreckage to the left. Use the 2 patches of Seaweed to keep out of sight from the sharks. Be careful as Eels are rampant in the area. Use the horizontal bar that is nearby to get a burst of speed and propel yourself forward to the next part of the wreck. Head on through the gap in the fore of the ship to find the second chest. Now replenish your breath. Head North and duck into the nearby seaweed to wait out the shark. When it moves away  Go to the East and enter the hull section to find the third chest of the area. Start upwards but carefully as there is a Moray Eel very close to you. Duck into the sea weed and then use the nearby air barrel to replenish your breath.

This part can be a bit tricky. Move into the wreck when the shark starts away from your position.  Swim through the corridor to the Northeast to reach the fourth chest. To reach the next one, turn around and head through the doorway behind you. In this short corridor, turn left to find the fifth chest. Once again, turn around and head through the new doorway. Swim to the Northeast then through the opening  to reach the sixth chest. This chest contains the Elite Mortar designs. Turn around immediately as Kenway is getting short of breath. There is an air barrel just outside so get to it presently.

From the air barrel things get riskier. The Animus Fragment sits at the top of the mast and there are numerous sharks around. Swim over to the mast and swim up along it to keep the shark's line of sight obscured. Repeat to get back down. Swim straight across to reach the next part of the wreck and go for the nearby air barrel. Replenish your breath then head through the doorway to the right of it. Go up the stairs but watch out for the shark just outside. When it turns away, go for the final chest. Now swim through the opening in the ship's hull on the West side. Go to the small wreck to find the final Animus Fragment. Just watch out for the Moray Eel that is nearby it. After that, use the nearby air barrel and make for the diving bell to finish this excursion.