The Ruins

From PotBS Wiki

In this mission you're requested to get some "evidence" from the ruined temple island of Cozumel (SW of Havana, will show up on your minimap anyway with an exclamation mark).

Sail (boat quality irrelevant, since it's gonna be avcom anyway) towards the island, once you get close enough you'll see the golden arrow, which will instantly transport your avatar to the island.

As soon as you're there you'll want to get into the jungle (btw, the atmosphere's just great), you'll come across several pieces of interactable environmental items that once clicked, a small popup will show up saying they're either too cumbersome, heavy or not useful enough to be carried back home.

Thus, what you really want to do is to run across the passages (minimap extremely handy) until you reach the ruined mayan city. Go up the stairs on the first, huge temple. Once up said flights, steer a bit left, go across some ruined columns, and then you should see a huge statue, with a golden idol encrusted on its base. Interact with it. Once you do, mayan warriors will spawn, which you'll have to kill, and keep killing, until you finally make it back, across the jungle, to your boat.

Good luck!

By El Bulto Loco, from Blackbeard.