Run down to the water.
Look over to the left, there is a chamber you have to reach.
Distract the giant alligator then swim over there.
Climb out on the left side.
Run around at the back to come to a broken bridge.
Jump to the other side.
On the right end you will find a lever on the left more skulls.
Attract the alligator by throwing skulls or jumping into the water again.
Then quickly pull the lever to catch the alligator in this chamber.
Jump back to the other side and run up the stairs.
Use the switch to open some gates and lower the cages outside.
Jump into the water and climb out onto the first cage.
From there jump towards the second.
Climb up to the top and jump onto the nearest chain.
Turn till the second chain is completely hidden behind the first.
Climb up a bit and start swinging.
Jump onto the second chain.
Turn to face the entrance.
Swing the chain and jump in.
Use the switch to bring down more cages and open more doors.
Jump back onto the last chain.
From there jump towards the cage on the left.
Climb up to the top of the cage.
Continue jumping towards the second cage.
From there jump onto the next chain.
Line up with the second chain, swing and jump onto it.
Turn towards the entrance, swing the chain and jump in.
Use the switch there.
Jump back onto the previous chain and from there towards the next cage on the left.
Take a running jump onto the next cage and again onto the third.
From here jump onto the chain in front of the entrance.
From the chain jump into the chamber.
Use the switch.
This opens the structure in the middle of the lake again.
Jump into the water and dive towards the platform in the middle.
Climb out and collect the artefact.
The floor collapses and you will drop into the water.
Cut through on of the passages with the machete and dive back outside.
The giant alligator will be released.
Hurry towards the platform where you entered the chamber.
Climb out and watch the cut scene.

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