Go to the left side of the cliff and you'll find a wooden pillar. Shoot a rope arrow at the ropes on the opposite side and make your way down.
Hide behind the first rock you see on the right and wait for the first Solarii to approch your area. Shoot him when he does. Now wait for the second one to come and investigate and shoot him too.
Now head for the platform near where you killed the guards and you'll see a zip line that goes up. Go to it and use it to get up to the tower.
Use the other zip line and slide down towards the boat and you'll find Reyes. A cutscene will begin.
Go around the beach one last time. Take anything you can find and upgrade your weapons. Again I recommend that you take the penetrating arrow upgrade for your bow and if you can afford it take the explosive arrow upgrade too. For skill I recommend having