From the diving bell locate the nearest Treasure and approach it carefully, avoiding the eel. Exit out the back of the wreckage and stay low to the ground using the seaweed to avoid the sharks. Swim left around the rock to another seaweed patch and a barrel for some air and then get the Treasure inside the next wreck. Head back out to the seaweed and when the shark is off to the right head for the seaweed on the left, using the burst beam to propel yourself forward. From here you should be able to get the Treasure inside the hull, while being careful of the eel.
Head back to the air barrel and then the seaweed patch. Turn toward the sharks location and look up into the rocks to spot another area of the ship. When the shark turns away to swim to the far side, swim up and left to enter the ship. Be wary of the sea urchins and swim down the corridor to another Treasure and then turn around and enter the door behind you for another Treasure. Once again, turn around and swim through a door and upstairs to the Treasure with the Elite Mortar Design Plans. With little air left, turn around and head outside to the air barrel.
You will now have a very risky swim up the mast to the Animus Fragment that will likely lead to an attack, if not death. Stick close to the mast and use it to break the line of sight with the sharks in the area both up and down and then swim down the other side to the hull or air barrel, whichever is closest or safest. Grab some air and then follow the deck of the ship to the final Treasure. Exit the west side of the hull and then turn south and swim to the burst beam to propel Edward forward, aiming for the Animus Fragment. Be careful of the eels in the seaweed as you enter and then head back to the diving bell to leave.
