Standard WSAD - movement.
E - interaction.
Shift - sprint.
F - flashlight.
1 - leave/enter boat.
ESC - pause.

Holding E, while on boat, but not controlling the boat, will allow you to preview amount of gas in engine. The same button will allow you to refill gas, if you find canister[s].

and most important one:
DO NOT WANDER OFF RIVER. Only leave boat for landmarks like huts (and torches).
Stay close to boat while on land, in case you need to run (escape).

If you hear sounds while on land, you are in danger. Quickly get back to boat, if you can.
Sounds generated while swimming aren't indications of danger. Just scaries.
If you leave control of boat, but stay on boat, you can still be killed.
Rule does not apply when you activated Xenolith by pressing Q (it always makes sound).

You only need to follow river and leave it three or four times.
a) gather Xenolith from third landmark (twin huts) and escape [gathering will spawn Old One nearby] (step might be optional)
b) collect one can of gasoline (landmark is torch with single hut with small fence in front) [there are more spots to find gas cans]
c) gather plane keys (single tent, at river's turn, is the landmark here)
d) get to plane and interact with it (obvious landmark as you go further with river)

Extra info:
If you get killed, you'll restart at checkpoint (finding Xenolith).

You are expeditioner trying to find something in Amazon. In your team there was a Lorenzo, dear friend, you are trying to find after waking up alone.

By trying to find how you were placed in this situation, you discover history only by notes left in some huts or their near area.
A mysterious stone dubbed "Xenolith" (Xeno + monolith) was found and since then strange things are happening. Apparently this released an ancient race named just "Old Ones", which started to murder people.
Close to Xenolith, protagonist feels being watched.

Lorenzo wanted to leave from Amazon early so he arranged plane. But his guide went nuts one night, never to be found again.
Supposedly Lorenzo lost keys to plane (why would he have them at first place), which you must pick up.
However, when you find the plane and try to reach for key, you find out that it's actually a knife!
Too much exposition on Xenolith apparently made your mind lost or controlled by "Old One". You commit suicide and fall into river (game suggest you do that in opposite order).

THE END.