Cannon T6i not turning on

Did you buy this new? Do you have a second battery to try? If not, try using a power adapter that plugs into the wall if you have one. IT sounds like you may need to consider that there was damage from the moisture near the waterfall. If that was the case, you could try keeping it in a very dry area. This next idea I am only suggesting because you are in the middle of a trip...You could try drying it out by placing it in rice overnight, to absorb the moisture. Just be sure to keep the lens caps on, and to wrap the camera in a thin towel or t-shirt, before you surround it with rice!!