38 miles in 12 hours in a river that has an average velocity of 3 to 3.5 mph.
Kudos to him for keeping the pumpkin upright in a difficult river, but I don't think he would have done quite so well in a lake.
On the other hand, a river with Class 3 rapids might have surface flow velocity of 10 or 20 mph, but that's not a good place to be in a pumpkin. Probably best to try this on the Missouri rather than the Congo....
Any of the rivers around here would rip that thing to shreds too.
The envelope math on that tells me almost all of his paddling went to controlling the pumpkin, not moving it forward, which makes sense for a round 'boat' and a single paddle. Some cultures have solutions for this but he wasn't aware of them.
Even a little shaping to make the pumpkin more oblong would net you quite a bit of velocity. In particular, the ribs on a pumpkin look a lot like hard chines on a kayak, if you cut open the side of the pumpkin [correction: he already did this, but on a round pumpkin, and then he sat 90° to the ribs] instead of the top. The next fool who tries this I expect to hit 40 miles in 10 hours, and then it's off to the races.
Kudos to him for keeping the pumpkin upright in a difficult river, but I don't think he would have done quite so well in a lake.
On the other hand, a river with Class 3 rapids might have surface flow velocity of 10 or 20 mph, but that's not a good place to be in a pumpkin. Probably best to try this on the Missouri rather than the Congo....