I'm going to call bullshit on the kid who claims to have walked the Darien... No offense, Dr., I'm just saying that it's not exactly the kind of place you can walk. For example, there are some huge fucking rivers to cross, and no, you can't just swim them. Especially because of the mud on the Pacific side. At high tide, the rivers are a mile wide. At low tide, it's a mile of mud. And it's the kind of mud that nobody can swim, not even Navy Seals, who, during the Invasion, died in the mud. If you get to Panama, you'll see the mud and the rivers.
The only way to walk the Gap is to do it down the middle, where the rivers aren't as wide, and then you take a cayuko down-stream to Yavisa, where you get arrested, which is better than dying.