As Jen studies her surroundings, anxiety beginning to claw at the back of her neck, it appears that the most straightforward means of getting across the river would be by shifting the the tree trunk. It's base and roots still rest on this side of the ravine, and it looks like at some point it had lain straight across the river, though maybe the current had shifted it to lay at a diagonal not fully reaching the other side.

As Jen ponders this, Frank calls out again. The voice replies, still across the river but closer now, it's source still out of sight. "Help! Hello? Here, come here!" the voice sounds strained and desperate.