The trio gets sucked into a swamp and then eventually separated. It's a terrible as it sounds.
As Sokka is being dragged away by the vines, she uses her machete to stop herself. The vines subside for a few seconds, but soon more return. They try to drag her away again. She hacks at the vines and is able to free herself. She returns back to where their campsite had been, and more vines follow after her.
"Aang!" Sokka yells slashing at vines. "Stupid swamp! Dumb, ugly vines. Katara!" She becomes caught and quickly slices herself free. "You think you're so tough, huh?"
Right after she says that she manages to trip on another vine which lands her right in the mud. When she lifts her head she sees an image of Yue in a beam of light not far from herself.
Sokka stands quickly, putting her machete away as she walks towards the beam.
"Hello? Yue?" With no reply Sokka turns away. "Trick of the light and the swamp gas." She says making excuses. "I hit my head earlier, so I'm obviously just seeing things."
Suddenly she hears Yue's accusing tone. "You didn't protect me."
Sokka looks around then rubs at her eyes. Now scared that a spirit might be there, Sokka pulls her machete back out.
Soon the trio manages to find each other. They also find the heart of the swamp. And then Sokka gets attacked by some swamp monster again. It's not enjoyable. Katara saves her, and then they figure out that there's someone inside the monster. Thankfully he ends up making things a lot easier for everyone by explaining what was going on in the swamp.
Sokka feels a lot better once they finally leave that place.