Sink or Swim

On the fourth leg of the expedition, the eight explorers struggle to stay afloat as they navigate the whitewater rapids of the Talachulitna River Valley. Weeks of unrelenting rain have flooded the valley's rivers, and the currents are gushing at dangerous speeds. Soon after landing, the explorers are faced with the pressing concern that they have no food. Expert climber Willi Prittie, Iditarod champion Dallas Seavey and his brother Tyrell will hunt the high country before setting out on the river. They plan to make up lost time on the river. But the rush to the finish leaves one explorer shipwrecked. Survival expert Austin Manelick and adventurer Tyler Johnson dart straight for the river. As the two most experienced packrafters of the group, they know the river is the fastest way to the extraction LZ. But even the most advanced rafters struggle with the river's beaver dams and logjams, and the men soon find this adventure won't be as easy as they hoped. Mountain man Marty Raney, his son Matt and dog musher Brent Sass decide to enter the Talachulitna River farther downstream from the rest of the crew. But even the shortened river route can't guarantee a safe trip, and it's not long before disaster strikes. Marty's raft flips, and he finds himself submerged in ice cold water. Facing the severe threat of hypothermia, the team must stop to get Marty warm, even if it means missing their flight out.