A good question. It's pretty tough for 4 wheeled vehicles to get across the Darien gap between Panama and South America. Driving is absolutely not an option - the track has been done I think twice by motorcycles, but that's it. Plenty of guerrillas in the midst of the jungle along with those horrific jungle conditions.
There simply is no easy answer, and plenty of horror stories about boats used to transport drugs using a vehicle as a bit of cover.
I've taken a motorcycle across the gap - the normal way, which means flying the bike from Panama to Quito or Bogota.
I've heard of flying or boating a bike around, but never anything as big as an RV. I imagine any option is going to be really expensive, though I suppose anything is possible.
Boat would be the only option for a rig as big as mine, and "really expensive" is a relative term. The cost of living full-time in a motorhome is highly variable and often has a very different shape than living a more stable life. When I'm doing very long trips, I probably spend more on gas in a month than most people spend on rent and food (I spent about $2000/month on gas during my Alaska trip, totalling about $5k for the whole journey). Spending $1000-$2000 for a ferry or ship to take my motorhome across wouldn't be what I would consider a show-stopping expense, and it's my understanding that that's the ballpark for this particular trip. It's just another thing to budget for. Moving, in a traditional fashion, to South America would probably cost even more, so from that perspective it's a bargain.
