Templar Hunt 01: Opia Apito

Mission 1: The Taino Assassin Head to the Castillo de Jagua area to find a Templar hunt at Cayman Sound (332,332). There are three ships in the area that will attack. With even a moderately upgraded Jackdaw, you should be able to take them down with ease. Swim to shore and head for the Templar hunt marker. The assassin, Opia Apito, challenges you to a hunting competition. You must kill and skin more hutia than her. Kill four hutia and a white jaguar attacks. Climb the closest tree or rock formation and hit the jaguar with a sleeping dart for an easy kill. Skin the jaguar to initiate a cut scene and complete the first mission

Mission 2: Templar Ships Head back to the Jackdaw, sail around to Grand Cayman (397,324) and dock at the harbor. Speak to Opia Apito who is standing on the docks. Follow her, then locate Alvin and eavesdrop on his conversation. When you reach the designated area, Alvin is standing in the larger group of people. Use Eagle Vision to easily spot him, then head to the top of the nearby hut to safely eavesdrop on his conversation. 

When the conversation comes to a close, kill Alvin and steal the ledger. Alternatively, you can sneak up behind him and steal it, but where's the fun in that? Once you have the ledger, the mission is complete.

Mission 3: Right Hand Man

Follow the marker to find Opia Apito and speak to her once more. Follow her again, then hide in the nearby stack of brush when instructed. When the target runs, chase him down. You don't have much time so stay as close to Vargas as possible. When he reaches the harbor, it initiates a cut scene in which he jumps to a ship. Your next objective is to reach the wheel of the Jackdaw and give chase.

Incapacitate and board Vargas' ship. It won't put up much of a fight, but watch out for fire barrels as you give chase. Board Vargas' ship and kill him for another cut scene to complete the mission.

Mission 4: The trail of Lucia Márquez Sail to Pinos Isle (332,469) to find two ships patrolling the harbor. You can take out one ship and swim to shore fairly easily, or you can take out both ships if you're feeling especially grim. Head ashore and speak to Opia again to begin the next mission.

Tail the guard. If you stay alongside Opia, you won't have much to worry about. Kill the guards ahead using the explosive barrel to the left, stealth attacks or a full frontal attack. Once the guards are down, Opia calls over a few more to entertain you. Make sure she's not under attack and take out the remaining guards, then chase down and kill Lucia Márquez. Every time she stops, she takes a shot at Opia, so kill her quickly. Once she's dead, the mission and side quest are complete.